More than Meets the Eye

By Jerry Dekay, Diagnostician

author5I have been with Certified Transmission since 2004 and in the transmission repair industry since 2002. Happily married for since 2006 with 3 boys 12, 8 & 8 (yes, they are twins). I enjoy cars, listening to music, movies, and bargain hunting. I am an ASE Certified Master tech and working on my L1 certification. I take pride in my work and plan to further my education here at Certified Transmission

 

Being fairly new to transmission diagnostics, I am always learning new techniques to try and simplify the process; however, at times it still can be overwhelming. I have spent the majority of my 14 years with Certified Transmission as an R&R technician along with spending roughly 1.5 years as a builder in the remanufacturing plant. I was successful working in these different positions, but they are more of a mechanical approach in the transmission repair field as compared to the electrical side I now see in my diagnostic role.

Roughly a month ago we had a 2010 Toyota Tundra Crew Max pickup with a 5.7L engine and an AB60 6-speed transmission come into the shop that had some shifting concerns. After reviewing the customers concerns from our check out sheet along with any of the vehicles previous work history, I had noticed that it was recently at a Toyota dealership to address the same concerns. The customer’s specific concerns consisted of an occasional no reverse, firm shifts and no PRNDL read-out on the dash, along with the check engine, traction control, ABS, and 4-low lights all on.

Before getting ready to go on a road test I scanned the truck and found a couple of transmission codes in the system: P0722 (Output Speed Sensor Circuit) and P0705 (Transmission Range Sensor Circuit Malfunction) along with doing a quick visual under the hood and underneath the truck. I saw that transmission work had recently been done. It appeared that the transmission pan had been removed, the MLPS switch looked new, and the Output Speed Sensor (OSS) also looked new. I also wanted to make sure these sensors had a secure connection to the wire harness which they did. Once I took the truck out for a road test, I could confirm the firm shifts and additionally noticed harsh banging engagements from Park to Drive or Reverse. I also observed 1st, 2nd, and 3rd gears but no commanded upshifts past 3rd. In addition, I was getting no OSS signal and no PRNDL information from the transmission. I pulled over and decided to clear the codes and see if the same codes came back and if I could get it to up-shift past 3rd gear. After the codes were cleared, they came right back and the upshift pattern had not changed.

Before digging into this electrical problem, my next action was to reach out to the customer and gain some insight as to the nature of the repairs previously done at the dealer and why he ultimately decided to have us to take a second look into his concern. A brief conversation revealed that the dealer had recommended a transmission replacement since replacing the MLPS and output speed sensors did not rectify the problem, and the customer wanted a second opinion.

Applying this new information, I wanted to confirm that these new sensors had a good connection to the wire harness with no damaged, broken, or corroded pins. After a quick check this showed no obvious concerns and I proceeded to move up the transmission wire harness which runs over the top of the unit and up over the top side of the bell housing to the passenger side of the engine compartment where the harness plugs into the module. About halfway up the harness that branches to the module, I noticed some damage to the split-loom wire covering and with an inspection mirror I could see what appeared to be where a critter may have chewed on the harness. At that point I let my manager know what I was seeing and requested some additional diagnostic time so that I could go further into this to confirm my suspicion that a transmission replacement is not warranted. The customer was happy to hear this and authorized us to spend a couple hours to repair the harness on retest.

Since the damage was somewhat hard to see, I unplugged everything on the harness and unbolted all the brackets securing it to the case of the transmission. I also had to remove the front driveshaft to give gain enough room to bring the harness to the side for further inspection and repair. This revealed a total of six wires with damage once I was able to open the harness. (Figure 1)

Article Figure 1Figure 1

 

Repairing the damaged wires was straight-forward and a new section of split loom tubing was spliced in and taped up. Once the harness and driveshaft were reinstalled, a road test confirmed a properly working and shifting transmission with no warning lights on the dash. Project complete! Or so we thought?

Fast-forward two-and-a-half weeks after the customer picked up the truck; we received a call from the customer stating the Tundra worked great, but now the same previous concerns had returned. Once the truck was checked back in at the shop, I did another visual check on the wire harness to check the recent repair and found no damage. A quick scan and road test revealed similar shifting issues as before except the PRNDL was working correctly this time. The only code in the system was for the OSS and scan data showed no signal. I pulled the output speed sensor to visually see if the reluctor in the transmission was turning with the output shaft (which it was) and while the sensor was out, I also checked resistance and it was within spec. (Figure 2)

Article Figure 2Figure 2

 

At this point I felt like the recipe was there to produce a good signal, but why wasn?t the computer reading it? Utilizing the Snap-On Zeus scope function and tapping into the output speed wires right at the module connector, I was able to see a waveform that varied with speed. (Figure 3)

Article Figure 3Figure 3

 

The signal that the sensor was producing was not familiar to me, so I looked at the component test information on the scan tool and compared the signal to what Snap-On suggested, and it was similar. (Figure 4)

Article Figure 4Figure 4

 

Next, I wanted to check the pin drag and retention between the module and connector before condemning the module as defective. The pins were in good condition and I found no issues there. Armed with this information I determined that the module must have sustained internal ECU damage from the handful of wires that had been previously chewed through and exposed. After the replacement module was installed the truck was back to shifting, correctly.

Whenever wires are exposed bare for any reason, they are susceptible to shorting out with each other. Sensitive electronics like the ECU have a low-to-no tolerance for power being applied to internal circuits where there should be no power. It would have been impossible to predict the eventual failure since the post-repair road test following the wiring repairs went without a hitch. In this case, it was a matter of coincidence and when all was said and done, the customer still saved thousands of dollars of unnecessary repairs in the form of a transmission replacement and was happy with the outcome.

Use Multiple Sources Of Information

By Daniel Skinner, Diagnostician

author5Daniel is a Diagnostician for Certified Transmission’s Blue Springs, MO shop.

 

 

 

 

 

Occasionally in diagnosing transmission problems technicians are faced with challenges that force us to look beyond the transmission control system. As vehicles become increasingly complex, it is crucial that we educate ourselves with all systems pertaining to the vehicle we are diagnosing. Many systems are tied together in one way or another and can directly affect performance and function across those systems if a malfunction is present in one of them.

It is also very important that we invest in more than one source of technical information. All too often I have encountered discrepancies in the information I have found while diagnosing a problem. It is up to us to be able to recognize incorrect and/or incomplete information that we are accessing. In many cases this can be time consuming but is a necessary part of our jobs. As vehicle manufacturers add more and more systems and integration, the importance of correct and complete information becomes even more important.

One example that I encountered was on a 2016 Ford F-150 4×4 equipped with 5.0L engine and 6R80 transmission. The truck was towed to our shop and the customer stated that it would not start. The customer was told by another shop that it was not showing proper gear selection. This prompted him to bring it to us, as it appeared to be transmission related.

Upon my initial evaluation, I found there to be a “no crank” condition. The range indicator in the cluster showed no selected range no matter what position the shifter was in. Four codes were stored in the PCM: P0706 (Range Sensor “A” Circuit Range/Performance), P0707 (Range Sensor “A” Circuit Low), P1702 (Range Sensor Circuit Intermittent), and P1921 (Range Sensor Signal). When those codes were cleared, they immediately returned when the key was cycled off and back on indicating that I had a hard fault. My immediate suspicion was a failed TRS (Transmission Range Sensor) which is an integrated part of the molded lead frame inside the transmission. This is where digging a little deeper and educating yourself becomes crucial.

I needed to prove that the range sensor was faulty. I began by checking for voltage (VPWR) to the transmission range sensor. This voltage is supplied by the PCM (Powertrain Control Module) and should be at or near battery voltage. I back-probed circuit LE111 (violet/green wire) at the transmission connector. To my surprise I found only 1.9V present. (Figure 1)

Article Figure 1Figure 1

 

Did I have a lead frame problem causing voltage to be low? I disconnected the transmission connector to take the lead frame out of the equation thinking it would change. That was not the case; I still had only 1.9V on circuit LE111. Could there be a wiring problem between the PCM and transmission connector? Possibly a pinched or frayed/damaged wire? At this point I back-probed the same violet and green wire in connector C1381E at the PCM. I found that there was only 1.9V on the circuit at that location as well. With the TRS out of the circuit, I now suspect the PCM is failing to provide the correct voltage to circuit LE111.

Before replacing the PCM I decided to review the manufacturer’s wiring diagram one more time. On the transmission controls wiring diagram, I nearly overlooked an important detail. On circuit LE111 there is a splice (S141). (Figure 2)

Article Figure 2Figure 2

 

The diagram shows a splice, but no other wires were shown coming out of that splice. Since the very purpose of a splice is to distribute a circuit to other components, this did not make any sense. After over an hour of searching for more information on S141, I finally found another 3rd-party wiring diagram with more detail about it. The diagram I found pertained to the electronic engine controls for the 5.0L. In that diagram I discovered the reason there is a splice in the circuit! S141 distributes voltage not only to the TRS, but ALSO to the camshaft position sensors! (Figure 3)

Article Figure 3Figure 3

 

The 5.0L engine utilizes two camshaft position sensors; they are located at the rear of each cylinder head, near the firewall. Could there be a faulty sensor or damaged wire bringing down the supply voltage provided by the PCM?

My next move was to once again back-probe circuit LE111 at the PCM. While back-probing with the key in the ‘on’ position, I disconnected the left bank camshaft position sensor. That resulted in no change of voltage on the circuit. I then disconnected the right bank camshaft position sensor, and bingo! Voltage on circuit LE111 immediately jumped up to 12.28V. (Figure 4)

Article Figure 4Figure 4

 

I had finally found the culprit: an internally shorted camshaft position sensor. (Figure 5)

Article Figure 5Figure 5

 

After replacing the faulty sensor and clearing the codes, the truck started and worked perfectly.

Keep in mind that there were no drivability complaints prior to the no crank condition, nor any other codes that might pertain to a problem with a camshaft position sensor.

The most frustrating part of this was the issue of not having the correct information. This is exactly why it is paramount that we have access to and use multiple resources for reference. If we rely on one source, be it manufacturer-provided information or not, sooner or later you will encounter a problem with the information provided. I have seen it with all sources. Had I relied on the initial wiring diagram, I would have never known that the camshaft position sensors were part of the circuit and probably replaced a part (or parts) that would not have resolved the problem. This would obviously cost unnecessary time and money.

Take the time to do the homework. Successful results and happy customers will follow.

6R140 R&D at Certified Transmission

By Chris Adams, Diagnostician

author1Chris Adams started with Certified Transmission in 1986 as an R&R technician, and currently works as our Diagnostic Trainer. His current duties involve training and advising our retail diagnosticians, as well as assisting in the research and development of our remanufactured products. He also holds ASE Master and L1 certifications.

 

 

 

One of my jobs at Certified Transmission is to assist with R&D on the vehicle side of things, whether it is for new unit development or for an existing application that we already build as a part of our continuous improvement initiative. I gather real-world driving data from a vehicle we purchase for the purpose and this data is then used for developing Dyno Department testing routines, specifications for the solenoid department, or for the needs of our Technical Director responsible for the unit in testing. This article is not going to be about a case study or a problem vehicle that we found an unusual issue on, but more about sharing information and specifications that we found that might not be found within typical information sources.

Several months ago, we were working on the 6R140 for the HD applications and doing some pressure testing and gathering a general collection of data to ascertain specific control strategy for this transmission. Aside from a scan tool that we can use to look at data, we also have a very expensive scope that we can record up to 10 channels at a very fast sample rate. The sampling interval on the following example is 10us or 10 microseconds (which equates to 100k samples per second), and we can record for about 60 seconds with no buffering. Also, in addition to looking at solenoid control, we can use Pico? pressure transducers to record pressure information as we did on this example. (Figure 1)

Article Figure 1Figure 1

This is a “zoomed out” recording of a 0-70mph run where the transmission shifted through all six gears. The data is as follows: Ch1. yellow, actual line pressure. Ch2. green, line pressure control. Ch3. red, SSA. Ch4. blue, SSB. Ch5. lt blue, SSC. Ch6. orange, SSD. Ch7. teal, SSE. Ch8. purple, TCC. Here is the Solenoid application chart from ATSG for reference. (Figure 2)

Article Figure 2Figure 2

 

While it is easy to see almost all the gear changes just by the activity of SSB as it cycles on and off for every change except the 1-2, how does it change from first to second gear? You surely cannot see anything else changing from this view; the only thing that happens on the 1-2 shift is SSC (the 2-6 solenoid) turns on. This is a NL (normally low) solenoid, so to see what happens during the shift we really need to have a closer look at the signal while zoomed in. (Figure 3)

Article Figure 3Figure 3

 

This single action is all that happens in order to make the 1-2 shift. SSC ramps from 15% to 35%, then to 85%, and then ramps down to 55%. The three NL shift solenoids (SSA, SSC, and SSD) in this unit are never electrically off, but hydraulically they are off at 20% – duty and below, and they are on from 28-85% with most of the time spent between 30-44% duty cycle. However, the NL TCC and both the NH (normally high) shift solenoids will turn off electrically. The other event that is not easy to see happens on the 4-5 shift with SSA, and that solenoid is on for gears 1-4 and turns off in 5th and 6th. There is no good way to visually illustrate this, but in 1st through 4th gears SSA is on at about 56% duty cycle, and around one second before the 4-5 shift completes by SSB turning off, SSA starts ramping down from 56% to 10%. The takeaway with this is that you really need to use a scope if you are trying to look at any type of solenoid activity; a DVOM is just not practical to use on an application like this.

The other thing you might notice from Fig. 1 is the line pressure. The top line is a direct voltage reading from a Pico? WPS500X pressure transducer. During each shift transition (and when TCC applies), you can see a jump in the line pressure. This recording is just a normal acceleration event from 1st to 6th gear. The shifts completed at about 2000 RPM with line pressure at 100-105 PSI, and during each shift the line pressure jumped up to 140 PSI. When TCC applied, it changed to 167 PSI. When we talk about shift adapts this is the area where you are going to see a change in these pressures. These changes in pressure are not going to be the same from one unit to another. For example, on a high-mileage unit you will undoubtedly see these pressures raise higher than this, whereas on a fresh remanufactured unit, a unit where there were modifications made to the VB, or even a unit utilizing a more aggressive clutch material, you could possibly see the pressure go down during a shift transition rather than up like what we saw here.

The TCC solenoid when activated changes from 85% to 55% to 40% in about two seconds and will fluctuate depending on load anywhere between 10% to 55%. The only time you will ever reach the maximum line pressure is while performing a reverse stall test. (Figure 4)

Article Figure 4Figure 4

 

As you can see, the line pressure solenoid turns off and line pressure shoots to 285 PSI. For more reference material, look at Fig. 5 for line pressure vs duty cycle, and Fig. 6 lists all solenoids and the frequencies that they operate at. (Figure 5 & 6)

Article Figure 5Figure 5

 

Article Figure 6Figure 6

 

Hopefully, this article has provided more insight to the control aspect of these modern transmissions. While we use this data in order to fine-tune our dyno testing and help improve our products, it can also be used for diagnostic purposes in the field. As the controls become more precise in nature, scoping equipment becomes a necessity in any shop that is working on late model vehicles.

Don’t Forget the Dowel Pins! This Part Can Make or Break Your Installation

By Zack Harkins, Diagnostician

Zack has four years of automotive industry career experience and has spent a year as an automatic transmission specialist. He is currently a Diagnostician for Certified Transmission at our Grandview, MO facility

I transferred to this shop location late last year to take over for a diagnostician who was moving. One the vehicles he left for me was a 2006 Nissan Murano AWD with the RE0F09A CVT transmission. The issue with this vehicle was a leaking passenger side axle seal from the PTU. The seal had been previously replaced but it was still leaking gear oil. It was discovered that the seal alignment was wrong and was then replaced with a new one. The PTU was topped off and driven for several miles, and when double-checked, it appeared to be dry, so the vehicle was delivered back to the customer. The customer called back a few days later and said it was leaking again and brought it back to us.

Confused, we pulled the axle again and inspected the seal. We noticed that it was leaking CVT fluid at this point. The dust shield on the axle had cut the outer part of the seal but should not have affected the part that seals the axle itself. Looking inside the PTU, we could see that the seal inside the PTU was ripped. This is a common issue on these PTU’s and has a TSB from Nissan: NTB10-123.(Figure 1)

Article Figure 1Figure 1

 

After informing the customer of the issue and the known problem, she agreed to install a used PTU. The used unit was inspected for any seal damage and appeared to be intact. The Murano was reassembled, filled with fluids and taken out for a drive. After returning from the test-drive there was a small amount of fluid around the lip of the seal. The axle was pulled again, and everything was visually inspected. The axle was checked for scoring, the intermediate shaft, bearing and bracket were all inspect for deformity, and all mounts were also checked. Nothing showed any signs of being damaged. The conclusion was that something had to be wrong with the used PTU and Nissan was contacted to deliver a new one to us.

The next day the new PTU was installed but the result, unfortunately, was the same. Now I was feeling defeated; nothing was adding up, so we reached out to our headquarters to brainstorm and called the customer with more questions about the vehicle. After making certain that there was nothing wrong with the axle and knowing that the PTU was new from the factory, and ensuring that there was no seal damage, we learned from the customer that the CVT transmission had been replaced with a used unit three years prior. A possible clue!

Upon closer inspection of the transmission installation everything appeared to be installed correctly, but one thing stood out. The paint from the parts yard looked like a sliver of it had been scraped off on one side of the inspection plate. After securing permission to pull the transmission from the customer, the removal the culprit and the crux of this article.

When the used transmission was installed, the installer failed to replace the rear dowel pin that was left out. (Figure 2)

Article Figure 2Figure 2

 

The transmission had sat in place perfectly for three years and then one unknown event was enough to turn the transmission a fraction of a degree and cause the PTU to sag on the axle and allow the seal to leak. A new dowel pin was installed, everything was reassembled for the last time, and the customer was thrilled to have her vehicle fixed. This was a headache that had a happy ending but could have just as easily ended poorly.

The dowel pins are probably one of the most neglected and overlooked items when it comes to installing a transmission but is also one that can cause catastrophic problems that aren’t easily pinned down. A technician can get frustrated when they can’t remove the old ones from a transmission and not want to wait for replacements, or the pins can simply get lost in the process of removal. No matter the reason or inconvenience, it is not worth the cost and damage you can do to that brand-new transmission you are installing for the customer.

The general assumption would be that these do little more than assist with the installation process and that the bolts are used to properly align the transmission to the block. Why wouldn’t it? How are two pins supposed to do what 8-12 bolts can’t? As we just demonstrated with the anecdote above, the tolerances and angles of transmission these days are extremely crucial and the ability for a transmission to move millimeters can throw the whole system off.

We were fortunate that the signs were as obvious as a major leak, but the affects can be far more subtle while destroying this investment. By not having a snug and precise alignment, transmissions can experience a myriad of issues, including: vibration while driving, premature wear or damage to the crankshaft pilot, torque converter pilot, transmission front pump, torque converter pump hub, internal transmission bushings, and misalignment between starter pinion gear and ring gear on the flexplate.

The dowel pins are solely responsible for properly aligning and locating the transmission onto the back of the engine. The dowel pins as well as the pilot holes in the transmission case, should be thoroughly inspected for any wear before final assembly of the transmission to the engine. This will ensure correct alignment and prevent premature failure of any of the potential wear items listed above.

This is a healthy reminder to ensure that you are always installing items properly and how the smallest thing makes a difference. At the end of the day, those extra 10 minutes or few dollars can save you a comeback, a warranty situation, or prevent keeping the customer happy knowing that the job was done right. These details matter.

Recreating Environmental Events Factors Into Diagnosis

By Brent Brown, Diagnostician

Brent has been in the auto industry for 8 years, 2 of those with Certified Transmission. He has been married for 9 years with three boys. He enjoys reading and sketching in his free time

 

 

 

 

 

A customer came to our shop with a 2010 Ford Fusion equipped with a 2.5L engine and a 6F35 transmission. The customer had a concern of the vehicle banging into drive and reverse intermittently, along with lack of acceleration when this would occur. On my initial inspection I found the fluid full and in fair condition, with no leaks seen anywhere. The computer had a history of code P0754 (shift solenoid “A” intermittent), but no active codes. I test drove the vehicle while monitoring commanded gear, torque converter slip RPM, output and input speeds, shift solenoid “A” command, and shift solenoid “A” voltage. The transmission operated as designed without setting any fault codes or having any noticeable harsh engagements.

We notified the customer that I would need to spend more time with the vehicle to try and recreate the fault conditions. This would help me determine what route we needed to take with the diagnosis. I did some research and found the solenoid should be off in park, reverse, and neutral. It is only commanded on from first through fourth gears, and then is turned back off in fifth and sixth gears. I then took the vehicle on an extended test drive of 30 miles trying to get the vehicle to shift as much as possible from fourth to fifth gear. I wanted to see if the solenoid was staying on when it should shut off, or if it was turning off when it should be on. Again, the vehicle operated perfectly with no faults. Using the scan tool, I was also able to command the solenoid off and on and could hear the click from the transmission, showing us that the solenoid was electrically working.

I then wanted to find out from the customer when exactly the vehicle was acting up. I wanted them to talk me through their drive each day to try and find a pattern. Well what seemed intermittent to them actually had a pattern they just hadn’t noticed. It would sometimes act up as soon as the left their house, only after they would start their car and let it warm up. If they started out cold it would drive okay. When it acted up while they were driving, it would be in stop and go traffic. If they were on the open roads with no stopping it would seem to work fine. I was able to see a pattern. If the vehicle could run with little to no under-hood cooling from air movement, it would start to act up. I ran the vehicle in the shop since I wanted to see how long it would take for the solenoid to act up, so I chocked the tires, set the parking brake, and let it idle in gear while monitoring shift solenoid “A”. Within 15 minutes the solenoid would start cutting out and the vehicle would set the P0754 fault and go into fail safe. I had finally recreated the circumstances that caused the vehicle to act up. Now I had to be quick with my testing so I would not lose my conditions. (Figure 1)

Article Figure 1Figure 1

I started with checking continuity from the PCM through the transmission. I found no open in the circuit. I tried wiggling all connections to see if I could get the connection to break. The circuit held and never went open, and it was showing 5.19 ohms for the transmission temperature of 163°F, which according to Ford specs was correct. I also did a load test with a headlight to see if it could maintain voltage, and it did. I then proceeded to check all connections for fitment and to make sure there was no moisture or corrosion. I found that pin 22 on the C1520A trans-axle vehicle harness was recessed compared to the rest of the pins. When I checked it, I found I could push it up and down and that it wasn’t fully snapped into the connector. I assumed this was my problem and figured it was just barely making connection, and when the harness would get hot, it would start to lose connection. I reseated the pin and made sure it had no movement; I then cleaned the connector and applied dialectic grease. In my mind I was sure I had found the problem and was sure the issue would be fixed. I reconnected everything and set the vehicle up to run again, in gear, while monitoring the problem solenoid. Within ten minutes the solenoid was cutting out and the vehicle went into fail safe again.

I was at a loss; everything had checked out! The circuit was good and I could command the solenoid and hear it activate. The vehicle performed great until it got hot under the hood. The only thing left was the computer. It was the only other thing that made sense. I then let the vehicle cool back down and made sure it was operating as it should. I applied heat directly to the computer using an industrial heat gun to raise its temperature quickly. Within a few minutes the solenoid started cutting out. (Figure 2) I had found the culprit! I replaced the computer and programmed it to the vehicle using FJDS. I performed my test one last time. I once again ran the vehicle, in gear at the shop, while monitoring the solenoid. After 20 minutes of continuous running, I had no fault. I test drove the vehicle through neighborhoods trying to maintain low speeds with as much stopping as possible. The vehicle performed normally. (Figure 3)

Article Figure 2Figure 2

Article Figure 3Figure 3

We delivered the vehicle to a thankful customer that was pleased and excited that they didn’t need a new transmission. The difficult part about diagnosing a defective controller is that it’s essentially a black box; there is no information regarding the internal circuitry, so you’re left with acting on a hunch and trying to recreate an environment as I did, or just taking an expensive chance by replacing it. Knowing the primary trigger of the issue is the key to a successful diagnosis.

Mild Lift On Jeep Causes Transmission Issue

By Paul Loch, Diagnostician

Paul has been an ASE Master Certified Technician for several years. He has been with the Certified Transmission team since 2010.

 

 

 

 

 

 

 

In late 2019 we had a customer bring us a 2014 Jeep Wrangler 4WD, equipped with the 3.6L engine and the NAG1 transmission (722.6). The customer’s concern was that it would not shift. Like every vehicle that comes to us, I started off an evaluation which is a predetermined set of initial procedures that are performed on each vehicle we look at.

I brought the Jeep into the shop to do the visual inspection and to check fluids which all looked good. I then proceeded to check the battery, starting, and charging systems which we refer to as an ESA (Electrical System Analysis). The Midtronics ESP-1000 came back with no issues found. I then performed a road test to attempt to duplicate the problem. I connected the scan tool which is a Snap-On Zeus model to do a complete scan of all on-board modules, and I was able to retrieve several DTC’s as follows: P0430 (catalyst efficiency bank 2), and P0016 (camshaft/crankshaft timing misalignment). Both of these codes were stored in the ECM.

In addition, other codes pulled were U140A (implausible right front wheel speed signal received), U140B (implausible left rear wheel speed signal received), and P0501 (vehicle speed sensor 1 performance). These three codes were stored in the TCM. There were also six codes stored in the ABS module: C1015 (RF wheel speed sensor circuit), C1020 (LR wheel speed sensor circuit), C121A (steering angle sensor not initialized), C1027 (LR wheel speed sensor erratic), C123C (dynamic sensor mounting/installation performance), and C2205 (steering angle sensor internal).

I knew that a vehicle speed sensor code could cause a no shift condition, and I have also seen an engine-related DTC such as the cam/crank code cause similar concerns, but then I was thinking that this transmission only has the two speed sensors inside the transmission, on the conductor plate! I decided to clear the codes from all the modules. I then set up the scan tool with all of the appropriate data PIDS I felt were necessary to aid in diagnosing this Jeep, and went for a drive to see how everything works.

The vehicle was cold when I started, and at first it worked fine and shifted great for the first eight or so miles. As I continued to drive I came up to a railroad crossing, and it was after I went over it (a very bumpy crossing), the transmission suddenly went into fail-safe mode. I pulled over to the side of the road so I could review my data from the scan tool. The only PID from my data list I selected that showed anything wrong was one labeled “output RPM”; it had gone to zero. Given that this transmission doesn’t have an output speed sensor, I was a bit confused at first as to where this output signal was coming from. I decided to head back to the shop to begin diagnosis. When I drove back to the shop, I suddenly had up-shifts again. I never cycled the key or did anything to get it out of fail-safe, so was it ever in fail-safe at all?

I looked at the output RPM PID and it was reading just fine. I was paying close attention to the scan tool so I could capture a reading the moment it acted up. After driving down the road for another ten minutes with no issue, I went back to the railroad crossing that seemed to have caused it to go into fail-safe the first time. Sure enough, after crossing the rough tracks again the transmission stopped shifting and lost the output rpm signal. I did recheck for DTCs in all the modules again and the same codes were set in the modules except for the ECM.

Before I began driving again, I wanted to wait just like before to see if it would go back to shifting on its own. It did. I then went to a bumpy parking lot I knew of to confirm that the issue had something to do with bumps. Every time I hit a bump in the lot the unit would go into fail-safe. I then went back to the shop to look up some information on where this output RPM signal was coming from, and I really could not find a solid answer as to what the TCM used for this signal. I needed to press on. Since the left rear and right front wheel speed sensor DTCs did return, I decided to take a closer look at those codes.

After I raised the vehicle up on a two-post lift instead of the drive-on which I had used at first, I noticed the wires that were going to the rear wheel speed were being pulled and stretched very tight. (Figure 1)

Article Figure 1

Figure 1

All of the factory wire holders were in place, so I knew they hadn’t been tampered with. After I was able to unclip the harness, I peeled back the split loom where it was pulled and stretched the most and I found discoloration in the insulation. This led me to believe that the wire itself was barely connected by one or two strands. (Figure 2)

Article Figure 2

Figure 2

Since our lead diagnostician is always gathering information like this, I decided to put it all back just the way I found it and set up the scan tool to monitor the wheel speed sensor data and the output speed data, and I could pretty much prove that the output speed parameter was coming from the left rear wheel speed sensor. As you can see in the next image, at the same moment that the LR wheel sensor drops out the output speed goes to 8024 RPM which seems to be the arbitrary value that comes up on a FCA product when there is no signal. The “limp home mode” PID simultaneously changed to “set”, so it was in fact going into fail-safe! (Figure 3)

Article Figure 3Figure 3

When I got back to the shop and got the vehicle back on the lift I was able to pull on the wires, and it broke in half with very little force. (Figure 4)

Article Figure 4Figure 4

I repaired the wires and reinstalled everything except I left one holder unclipped so that it wouldn’t pull anymore. I discovered that this Jeep had a very small 2” lift-kit that was just enough to cause this wiring issue by pulling them tight. I drove the vehicle in all of the aforementioned conditions and the issue did not return.

After the repair was completed, you can see that the LR wheel sensor and the OSS parameters basically mirror each other, as they should. (Figure 5)

Article Figure 5Figure 5

 

I wouldn’t have thought a wheel speed sensor could have caused the transmission to go into fail-safe, but as they say, you never stop learning; there’s a new surprise around every corner.

Circuit Issues Cause TCM Codes

By Randy Peterson, Diagnostician

Randy has worked for Certified Transmission for over twenty four years and is an ASE Certified Master Technician, including L-1. He has been in the automotive industry for over 30 years.

 

 

 

 

 

A 2009 Ram 4500 was towed to the shop. This truck had the 6.7 turbo diesel equipped with our remanufactured AS68RC transmission. This vehicle was also equipped with a snowplow, salt spreader, performance tuner, and several communication radios. The vehicle ha a multitude of issues with diagnostic trouble codes stored in several different modules. After gathering the trouble codes, a road test was in order. I connected the scan tool and proceeded to drive the truck. Initially the transmission would not shift, and I noticed there was no input speed signal registering in the PID data. This coincided with the P0717 (no signal input speed sensor 1) code pulled. A trouble code P0560 (battery system voltage) was also stored along with a P2121 (accelerator pedal position sensor 1 performance). I quickly looked at the APP sensor and the scanner data PIDs confirmed that it was working at the present time, so I decided to address that issue after I addressed the transmission issues.

We investigated the P0560 code first. The theory of operation for this code is: “Battery voltage is supplied to the controller and is used to write to the controller EEPROM after vehicle shutdown (similar to Keep Alive Memory).” That seemed like a mouthful. We pulled a wiring diagram and discovered that B+ to the control module comes from the TIPM (Totally Integrated Power Module), fuse #4. Fuse #4 supplies B+ to the TCM (Transmission Control Module) at C2, pin 7. The easiest place to start is checking the fuse since the TCM is under the dash. Once the cover was off and the fuses visible, we saw that fuse #4 was missing. (Figure 1) We were unable to determine why someone had removed the fuse. Kevin replaced the fuse, cleared the codes and then scanned the codes once more. The P0560 was now cleared and did not return. It was time to move on to the next issue.

Figure 1

Now we were going to address the ISS (Input Speed Sensor) code. We still had no speed signal on the scan tool with the engine running. This speed sensor is easily accessible, so we decided to check it while it was still in the transmission. We noticed that the sensor connector was not securely fastened. He inspected the connector and the sensor pins and then secured the plug. This did not fix our issue. We then disconnected the sensor and tested the resistance of the speed sensor itself. The sensor in the transmission tested “OPEN” so we decided to replace the sensor. It was a difficult part to source. They were backordered from the O.E. but we were able to locate one.

The sensor came in a few days later and we installed it. To our dismay, there was still no speed signal on the scan tool. We tested the new sensor and it was good. We were missing something; could there possibly be issues with all of the added aftermarket components? Could the tuner have some effect on the sensor operation?

I had some idea of the direction I would need to go, but I had not worked on this system in the past. It was similar to others, but still different. This vehicle has an AS68RC transmission. This system uses a separate TCM that is located under the dash. This TCM had been replaced prior to coming in to us. All of the B+ and grounds were double checked, and the calibrations correct to the VIN were confirmed. We knew it had been replaced and confirmed that the install was correctly done. I printed out all of the relevant information I could get, including theory of operation, wiring diagrams, and pertinent specifications that were available.

These speed sensors are 8-volt magneto-resistive sensors that generate a square wave signal. It measures the speed of the P1 sun gear which is attached to the input shaft. What was confusing was that the first wiring diagram I looked at, C2 pin 1 at the TCM did not state an 8-volt supply.

In fact, C2 pin 1 was labeled as “speed sensor ground” on this document. That didn’t make any sense. As I looked further and I found a different diagram that was labeled correctly. Now that I had good information and a plan of attack, I started my search for the problem. (Figure 2)

Figure 2

I sensed that I was not having an issue with the 8-volt supply since we were not having any issues with the OSS (Output Speed Sensor), because both sensors get the 8 volts from the same source, C2 pin 1. Regardless, I thought I’d better check it in case there was an issue with the splice S021.

I tested and saw 8 volts at pin 2 of the ISS. I decided to scope the sensor at the speed sensor itself. I was able to get a pattern but there still was no signal shown on the scan tool. The pattern looked odd to me. The amplitude was very low, and I thought there must be something limiting it and perhaps why the TCM couldn’t register a signal. (Figure 3) I would later determine that I was wrong and started to head down the wrong path for a short period of time.

Figure 3

Figure 3

I thought that since the supply voltage was 8 volts, I should at least see 0-8-volt amplitude, or something close to that. In my basic thinking, if you are going to supply 8 volts you should USE 8 volts. Since most of the O.E.M.’s don’t publish their wave form specifications, I was not sure what I was working with or where to find it. So, I went back to double-check all my readings at the TCM. I rechecked all the voltages and grounds. Again, everything checked out. There had to be an issue with the TCM. The original TCM was in the vehicle so I swapped it back in and rechecked. No change in the results.

Racking my brain as to where I would find the crucial waveform information I needed, I looked through the PICO waveform library, and found nothing. I Googled it, and still found nothing. Out of the blue it occurred to me that I hadn’t checked the “Guided Component Test” on the Snap-On scanner. The specs I needed were found there! (Figure 4)

Figure 4

Per this information, the sensor should read .8V to 1.6V. That was precisely what my sensor was generating. Success! Not so fast, though. Why did I not have a PID reading on the scan tool?

I decided to attach my scope leads to the TCM. I back probed C1 pin 1, and C2 pin 1. With the engine idling there was no pattern shown on my scope. That’s a problem. Now I needed to figure out where the cause was. I knew it wasn’t the 8-Volt supply, because I had 8-volts at both of the speed sensors. I suspected an open circuit in the ISS wires (DG/OG). I started by working my way towards the transmission from the TCM. There is a bulkhead connector just above the master cylinder. (Figure 5)

Figure 5

I checked the TCM side of this connector, and still no signal. It was virtually impossible to back probe the back side, so I took the connector apart and checked the pin fit and made sure I had no damaged pins. I cleaned the connector and reassembled it, making sure the bolt that held the halves together was tight. I started the vehicle again and now had a good pattern and signal on the scan tool.

It seemed to be either a poor connection or the bulkhead connector bolt was not tight enough. It seems that lately connection issues are the source of many a headache. I drove the vehicle and the transmission worked well. I got a good recording of the ISS and OSS patterns for future reference. (Figure 3)

Figure 3

No codes returned. I was happy but something about this was bugging me. When I got back from the road test I hooked up the scan tool, homed in on the ISS PID and watched as I loosened the bulkhead connector bolt. Nothing happened at first, but when I pulled on the connector a slight tug caused the ISS to drop out. We didn’t lose any other data, just the ISS. I tried this a couple times and it was repeatable. I was now satisfied that I’d located the root cause. I tightened the bolt again, cleared the codes, and went for a drive. The ISS fault was gone and the P0560 did not return with the fuse installed.

The APP code, P2121, did not return during this visit, however, it did return a few weeks later and we replaced the APP sensor at that time.

Sometimes you think you’re on the right track only to find out you’re going down the rabbit hole. Some problems are very frustrating while you’re in the moment but, great learning experiences once you conquer them. The key is to retrace your steps, double-check, and think outside the box. Even the most difficult issues can be fixed.

Jeep Won’t Shift From Park

By Mike Greer, Diagnostician

Mike has been with Certified Transmission since 1996, and been in the industry since 1987. He is an ASE master Technician and has served as a Master Builder for the company in the past.

I am not sure about you, but I am not a big fan of getting into a job that someone else has already been working on and failed to resolve the issue. I was not aware of this when I got assigned to diagnose a 2009 Jeep Wrangler with a 42RLE transmission. I started my evaluation with the customer concern of “cannot get out of park at times”. I walked out to the vehicle with scanner in hand, opened the door and what do I see? The whole center console is out and in the back seat…ugh. The vehicle came to us from a used car dealership that has their own “mechanic”. What was I going to get myself into? I started to look around and try to see what had been done, and I saw a new shift cable, a new shift interlock solenoid, and a new brake lamp switch; it appeared that throwing a bunch of parts at it failed to “fix” this one.

After checking fluids and scanning vehicle for codes I decided to go for a road test, the Jeep came right out of Park so I tried it a few more times and it seemed to work fine, each time it came out of Park with no extra effort. I continued on with the road test to make sure that there were no other issues with the operation of the transmission, it shifted well, no slippage, and TCC operation is functional, everything seemed to be operating just like it should.

When I pulled back into the parking lot I put into park again and this time it locked into park, I could not budge the shifter. With the console already removed I could see the shift cable mounting bracket flexing when I tried to force it out of Park. It seemed that I finally experienced the customers concern! The scanner was still connected, so I looked at the brake switch and the interlock PIDs and they were both being commanded. Since the console was off I could physically see the interlock working, but it still would NOT come out of Park. I then blocked the wheels and got under the Jeep and disconnected the shift cable from the shift lever on the unit and I could not budge the shift lever, but from inside the vehicle the shifter and cable now moved freely. This confirmed that the problem was inside the unit. Perhaps if the prior tech would have taken a different diagnostic approach, they probably could have saved some money.

At this point the Jeep was sitting in the parking lot stuck in Park and I needed to get it into the shop, so before I pulled the driveshaft to accomplish this, I had a couple guys come out and “rock” the Jeep to see if it would come out of Park. It made a loud “pop” noise and then came out of park, so we pushed it into a bay and finished up the evaluation. I turned in the paperwork with the recommendation to pull the pan and valve body for inspection. The technician pulled the pan and it was clean, and vehicle only had 50k miles on it so I was pretty confident that we could fix this without having to replace the unit. I gave the tech some brief instructions and reminded him to put the shift shaft into manual low position before trying to remove the VB.

With the valve body removed and on the bench, I did not see anything blatantly wrong with the park mechanism, but upon closer inspection I noticed that the rollers on the Park rod did not seem to “roll” very easily. We had some parts sent up from our remanufacturing plant. I installed a new Park rod and the rollers moved freely so I knew something was wrong there, but was it enough to cause our issue?

When I was trying to spin each roller around on the original one, I saw it, there was a flat spot on one roller and on the other one there was one section that was pitted: (Figures 1 & 2)

Article Figure 1
Figures 1 & 2

I am not sure if it was just one roller or if both of them had to be in a certain position for it to bind up the park linkage like it did, but that would explain why the problem was not always apparent. I took a couple of pictures and sent them to our tech director for that unit mode; and asked if this was something we had seen before, and he stated it was not. There are a couple other things inherent with that unit involving Park issues, but the damaged park rod rollers was not one of them.

Using a remote camera to inspect the park pawl a little more closely, we really saw no other damage. Park is not something that you want to take any chances with. This unit was not one of ours; if it had been, we would have replaced the entire unit because we do not allow repairs for Park concerns in the field. Since this was the customer’s unit, we replaced the park rod put everything back together.
After the repairs were completed, I took the Jeep out for a good test drive. I stopped on a hill, engaged and disengaged Park several times in both directions, and it performed flawlessly by both holding park and coming out of park. It’s possible that this transmission had an issue right from the factory and just progressively got worse; nonetheless the new part got it right again.

The new park rod is still available from FCA Part# 4800283AA. Retail cost $26.85.

2010 Ford Mustang PCM Problems

By Richard Hart, Diagnostician

Richard is a Certified Transmission Diagnostician with 8 years in the automotive industry, and is an ASE Master Tech with L1 certification.

 

A modified 2010 Ford Mustang made its way into our shop, and it was sitting 4″ from the ground with a complete aftermarket exhaust system and wheels. When I was given the customer write up sheet it read, “It will not exceed 35 MPH, the same in reverse, and it jerks hard.” 35 MPH in reverse…really? Maybe that wasn’t really what he meant, but that is how I read it. Upon further investigation into the history of the vehicle it revealed that another shop ran into the same issues and said it was fixed. Wonderful; I had apparently inherited someone else’s come-back. That never happens, right? The customer also stated that the problem had been intermittent for one or two months and had had a solenoid pack installed a couple of months ago.

When I first started the engine, the car jerked and moved forward 5′ and then neutralized. I noted a hydraulic pump whine also, and when I brought it into the shop I first checked the fluid and found no fluid coming out of the standpipe on this 5R55S transmission. This Mustang had 96,000 miles on it, so I thought surely this wasn’t a serious electrical issue. When I scanned for codes I found three electrical codes: P0778 (PC solenoid B), P0798 (PC solenoid C), and P0966 (pressure control solenoid B control circuit low). There were also mechanical fault codes for all the shift solenoids A, B, C, and D: P1714, P1715, P1716, and P1717.

I then added three quarts of transmission fluid, and when it started coming out of the overflow I smelled burnt fluid. I then printed the code list and cleared codes. The pump whine was still present and the vehicle neutralized after five minutes of putting around the parking lot. It seemed that this one would be pretty simple; obviously low hydraulic pressure is causing the codes. The fluid was really burnt so there was no chance of fixing this one in the vehicle, so I recommended that the unit be replaced.

After we sold the job, the R&R tech installed our remanufactured unit a few days later, and pulled it around to the front of the shop for me to finalize the job. I pulled the car into the shop and checked to make sure the calibration for the PCM was current, and it was. So now it was time for the final road test. While backing out of the shop the transmission neutralized again, so I shut the car off then turned it back on and I was able to go forward and reverse. Against my better judgment, I decided to drive it on my designated route and had no issues. Arriving back to the shop, I told my coworkers that there was more going on with this vehicle and I needed to continue to diagnose it. I explained what had happened and wanted to let it sit overnight before trying it again.

The next day I drove the vehicle a little harder and the transmission was slipping in 2nd and 5th gear under heavy throttle. No diagnostic trouble codes were present so I needed to attempt to replicate the issue before I could go any further. I backed the car out for the second time and it neutralized again. The work day was over so I figured I’d start fresh in the morning.

I went to bed that night and had a dream about a headless horseman in a Mustang; how weird was that? Getting back into it that morning, I decided to take a different approach and re-evaluate everything. I really needed to go over the ‘On Board Diagnostic Parameters ID’s’ (PIDs) with fine a tooth comb like I should have done the very first time this vehicle neutralized in the shop.

I set up the scanner with a data list and went for another road test. The MIL illuminated and DTC P0798 (EPC solenoid), P0970 (EPC solenoid circuit low), and then the P1714, P1715, P1716 and P1717 codes that the car originally had pulled up. As I was watching the data stream, some strange PIDs occurred at 2100 RPM sitting still (Figure 1). The vehicle neutralized for a split second before jerking forward. At this point I needed to look over the electrical codes once again and see what solenoids are on when the vehicle is in drive.

Figure 1

Moving forward, I knew that both SSA and SSD should be on for 1st gear. I noticed in 1st gear that SSA was on, and SSD was off. Only until I reached about 2100 RPM, the vehicle jerked forward, spun the tires, and then everything functioned properly electrically. Both SSD along with SSA were on at this time. On the solenoid apply chart (Figure 2), 1st gear SSA on SSD are on, and all other gears have a minimum of two solenoids on. Only having 1 of 2 shift solenoids required to be on places the transmission in an unknown state. I watched the pressure control solenoids when I had no movement in first gear; when watching pressure control ‘B’ solenoid it was high when it should have been variable. Once I started looking at the pressure control solenoids, I realized pressure control solenoid ‘A’ didn’t always do what it was supposed to do in each desired gear. If you have a PCS (pressure control solenoid) always open, the system is dumping hydraulic pressure and not sending it where it is supposed to go. This would cause lower line pressure at times and will allow clutches to slip under heavy load. The pressure control solenoids are a Variable Force Solenoid (VFS) type. The VFS is an electro-hydraulic actuator combining a solenoid and a regulating valve.

Figure 2

I set up the component test with the Snap-On Zeus so I could control the solenoids while watching the result with the scope. I noticed that some of the pressure control solenoids never came off ground when they were supposed to, or also would not pull all the way to ground while they were regulating. At this point I knew we had a controller problem. Now I had to prove it with the scope while the vehicle was commanding it.

With the scope connected, this is what I saw: (Figure 3). With the PCM commanding control not going through the component test menu, Ch. 2 (green) is connected to PCA which is being controlled, but SSA (Ch. 1) and SSD (Ch. 4) are sitting at ground. I then realized that when some of them were shorted to ground, the only way I could reset the circuit or gain functionality again was to unplug the PCM and plug it back in. At this point, with the scope hooked up and using the component tests, I could toggle the circuit with the scan tool a few times before randomly a few pressure control solenoid circuits would stick to ground or only reach five volts of B+ voltage available. I didn’t know what else I could do to prove to myself that this was a PCM problem, and as turned out, proving the Mustang needs a computer wouldn’t be my only challenge.

Figure 3

Two weeks and a couple grand later, the new PCM arrived. I followed the instructions on the removal and replacement of the PCM to a ‘T’. As most of you know, if you want to remove and replace the PCM with the IDS or FJDS you need to use the PMI function (programmable module installation). During this process I received a, “testman user error” and ended up locking the computer. I then made a call to the aftermarket manufacturer of this PCM and told them what happened. They advised that their computer was already programmed and just needed the PATS relearn done, and I was advised that I didn’t follow “their” instructions and had followed the OE procedure instead. I informed them that the PCM did not have any type of instructions with it, so they agreed to send another PCM out to me.

In the end, the new PCM solved all of the transmission-related issues. I received the replacement PCM and completed the PATS relearn. If you do any type programming on a regular basis, you know that Ford has had some issues with a “Testman” error from the late 114.xx version, and at the time of this writing, they are at 115.3 and I believe that those issues have been fixed.

2006 Kia Spectra No-Shift Concern

By Allen Channel, Diagnostician

author32Allen grew up under the wings of his father. He worked in his father’s shop starting out washing parts and cleaning. He soon was working on cars, but more specifically, transmissions. He eventually took over the business and ran it for many years. He later went to work for a Chevrolet dealership performing most of the transmission repairs. He left his native state of Ohio and joined Certified Transmission in May, 2015. He is currently our diagnostician in our Blue Springs, MO location.

A couple of months ago we had a customer come into our location with a 2006 Kia Spectra equipped with the 2.0L engine and an A4CF2 transmission. The customer’s concern was that the vehicle would not shift at times. I started the evaluation by checking all the fluids, doing a visual inspection, and conducting a battery and charging system test with the Midtronics analyzer, and everything checked out good. I then moved on to connecting the scan tool to the vehicle and checking all modules for DTCs; the only one that came back was a P0748 (linear solenoid) electrical problem. There was no freeze frame data stored; it probably wouldn’t have helped me with this issue, but I wanted to see if it would at least show the speed or temperature at which the code set. From the customer’s description it sounded like an intermittent issue.

I then cleared the code and set up a data list to record prior to the test drive. All of our locations have Snap-On Zeus workstations, and one thing this tool does really well is record data. It records the whole time you have a data list on the screen and gives you the ability to save the snapshot for later viewing using the free ShopStream software. All values referenced in this article came from ShopStream. The software is really easy to use and can be very helpful for reviewing data, especially when you don’t have a helper to drive the vehicle so you can watch the scan tool.

With the scan tool ready and loaded I went off for a drive. I had to come to a stop shortly after I started the test drive, so I looked at the graph I had on the screen for the linear solenoid and it was just a straight line at 0% (Figure 1).

1910a

Figure 1

The code must have set before I had the data up on the scanner because it never showed any higher than 0%. You might also notice that the vehicle never stopped shifting for this entire test drive when looking at the second and third graphs which are the ISS and VSS, respectively. I pulled over and cycled the ignition and the solenoid duty started out at 100% and quickly dropped down to zero probably in less than two seconds, but this time when I started driving again it had defaulted to third gear and would not shift (figure 2).

1910b

Figure 2

After returning to the shop I tried to command the solenoid on with the scan tool, and it did respond. I could hear clearly that the solenoid was pulsating inside the pan. I checked the connector at the transmission looking for a loose pin or corrosion, but all was good there. I then checked the connector at the transmission control module and it looked good too. With the transmission control module and the transmission connectors both off I decided to check the solenoid wires in the harness, and both wires checked good with the DVOM. With both connectors still disconnected, I applied 12 volts to the wires and put a load on them with a headlamp just to ensure they could handle a load. No issues discovered here. After this test I decided to put both connectors back on the transmission and the transmission control module and then try to pulsate the solenoid with the scanner. This time the solenoid did not work at all, so what the heck changed? I had proven that the wires were good, so was it the transmission control module or was it inside the transmission?

Next I removed the transmission connector and checked the resistance at the transmission from pin 9 to pin 10, which are the supply and control wires going to the solenoid. The circuit tested open. Now I knew the problem was inside the transmission but needed to determine whether the solenoid or wiring was at fault. It was time to remove the pan for inspection.

After the pan was off and the filter was inspected for any debris that might possibly warrant replacing the unit rather than repairing this one, I checked the solenoid itself. It tested at 3.5Ω, which is within specification. I then put 12 volts directly to the solenoid momentarily (remember the Ohm spec on this solenoid was only 3.5Ω and is duty-cycle controlled), and it seemed to operate when I did that. I checked the wiring (printed tape circuit) and both wires checked ok with good continuity. Seriously? Now I had to stop for a minute to gather my thoughts.

I decided to jump both of the solenoid wires together and check the continuity one more time and with both wires being tested at the same time, they were ok until I moved the printed circuit tape ever so slightly and then the circuit went open. Finally I had isolated the problem; the printed circuit tape must have had a break somewhere between the case connector and the solenoid itself (Figure 3).

1910c

Figure 3

I replaced the printed circuit tape, reinstalled the pan and filled it with the appropriate fluid. A final road test confirmed that the transmission was working properly. The code did not return after several test drives. The scanner was now showing solenoid duty working from 31% to 98%, and operating as designed.

Even with thorough diagnosis, sometimes it’s hard to isolate electrical faults like this when it’s nearly impossible to recreate the operating dynamics during static component and circuit testing. Components and wires do move around under normal operating conditions, and therefore tapping, pulling, and wiggling these items when testing is a must. That action uncovered the fault in this case.