Beware of Technical Misinformation

By Randy Peterson, Diagnostician

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

As with most of the accounts we’ve shared detailing vehicle symptoms and repairs, electrical issues seem to be the most common root cause. Our subject today involves a 2003 Dodge Sprinter 2500 that showed up at our door with the customer informing us that they could not shut it off since it would not restart without jumping the solenoid on the starter. The gentleman stated it would not start with the key, the shifter would not come out of park and the transmission would not shift. He also stated that we had installed a TCM approximately a year ago, and since it did not shift the customer thought it was related to what we had done. He also stated he had replaced the fuse in the fuse panel for the transmission and that didn’t help. Apparently, we needed to diagnose some electrical problems.

I began this adventure by scanning the computers for codes. There was a grocery list of codes stored and several communications (U-type) codes including, “No Communication from TCM”. I confirmed that the starter would not crank by cycling the key. I was told it would start by jumping the solenoid, so I knew there was battery power to the starter. Examining the wiring diagram for the starting circuit, I determined that I would need to start by checking the circuit at the starter motor relay.

I observed battery power to the relay pin 87 and pin 86 in the “crank” position. When I cycled the key, however, the ECM was not grounding the relay at pin 85. I replaced the relay with a relay jumper (see fig. 1) so I could easily start the vehicle to test it and move it around. But I needed to find out why the ECM was not providing a ground signal to the relay.

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Figure 1

The ECM was located and a quick visual inspection revealed heavy corrosion on one of the connectors. The ECM terminals and the pins in the connector were in poor condition. I thought maybe the connector would need to be replaced. The connector was cleaned and I also cleaned each pin in the ECM until the corrosion was gone. The terminals in the connector were not as bad as originally thought. As I reconnected the ECM I was hopeful that this would fix the vehicle. Unfortunately, that was not the case. The engine still would not crank while cycling the key.

Studying the wiring diagram more closely, I concluded that there must be some input causing the ECM to inhibit the ground to the relay to allow the starter to energize. If I bypassed the ECM and grounded pin 43 (see fig. 2), the vehicle would crank and start. However, the shifter still didn’t work. I needed to figure out what inputs the ECM used to determine whether to inhibit or allow the crank event. I also needed to address the “No Communication” code in the TCM (see fig. 3), hoping that resolving that issue may take care of the other symptoms also.

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Figure 2

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Figure 3

I double-checked for B+ at fuse #2 (see fig. 4 & 5), which was the one that the customer replaced. It was the only new fuse in the fuse box. I checked the fuse box cover and it confirmed the fuse replaced should be the transmission fuse. Examining the wiring diagram of the transmission power distribution, I could see that the transmission relay powers the TCM and the shifter assembly. A bad TCM relay could certainly cause the customer’s symptoms, so I checked my voltage and grounds at the TCM. I had no B+ at pin 29 (transmission relay output). I located the transmission relay and discovered that no B+ was present at pin 87 (should be hot at all times), but did have B+ at pin 86 with the key in the run position.

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Figure 4

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Figure 5

Tracing the red wire from the relay box (pin 87 of the transmission relay) to the fuse box under the seat, I found that the wire did not go to the fuse marked “transmission” (fuse #2) as the diagram indicated it should. Instead, it lead to fuse #4, which turned out to be the actual transmission fuse (see fig. 6). There was B+ at the fuse but nothing coming out of the fuse. The fuse “looked” ok. I cleaned the terminals in the fuse box, replaced with a new fuse and everything started working. The engine cranked and started. The shifter interlock was now functioning correctly. After clearing codes and road testing, I confirmed that the transmission itself was now operating correctly as well.

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Figure 6

Since the TCM was not powering up, it could not provide the signal required to allow the ECM to enable the starter crank circuit, and in addition, provide voltage to the shifter and transmission.

The most difficult part of this diagnosis was the lack of accurate information. I was misled on several occasions because the manuals were incorrect, and had to back track to figure out what went where. Incorrect wire colors and wrong pin locations make diagnosing difficult. It’s a part of our industry. After studying the diagrams running the test, if you don’t get the results you were looking for, you may have to start at the beginning and work your way through it. Had I tested all of the fuses in the beginning, I likely would have found the issue then. As they say, hindsight is 20/20.

The Case of the Cold TCM

By LJ Porter, Diagnostician

porter-ljLJ has worked for Certified Transmission for over 20 years and is an ASE-certified technician in transmissions, transaxles, manual transmission, steering, suspension and brakes. He was a remove-and-replace (R&R) technician for 6 years and has been a diagnostician since 1996.

A couple months ago we had a customer contact us about a problem that he was having with his 2000 Nissan Frontier 4wd Pickup. While he had some trouble explaining the exact symptoms that were occurring, we understood that the problem only seemed to happen when it was driven first thing in the morning, and that in simple terms, “it just didn’t want to go”. We arranged an appointment for him to drop off the vehicle with us so we could perform our initial diagnosis and evaluation after the vehicle sat outside overnight.

On the initial road test the truck seemed to drive out okay, but there was what I felt to be a slight bind up on the 1-2 shift with all else seeming normal. The next step was to get the truck into a service bay, check fluid, do a battery and charging system analysis, undercar inspection, and scan for codes. The findings of this initial evaluation indicated that the fluid was full but dark, and had a very slight burnt odor. The following codes appeared: P0325 (knock sensor), P0720 (VSS), P0725 (engine speed sensor), and P0732 (gear ratio error 2nd). There were no signs of water or glycol intrusion into the unit. While having an engine side code that related to an engine speed sensor and also the knock sensor code, I felt at this time the best course of action would be to refer him to a general repair shop to complete the engine drivability diagnosis.

The repair facility phoned us after they completed the engine-related repairs and said that there still seemed to be an issue with the transmission, so we went down and picked up the truck for further evaluation. While I could not reproduce the P0732 code, it still had a bind on the 1-2 that kept getting worse the more that I drove it. At this point, I recommended that we install one of our remanufactured transmissions. The manager sold the job and we got the transmission installed, completed the road test procedure, double-checked the complete repair and the truck was delivered to the customer. A few days later the vehicle owner called us and said that the issue had returned and the vehicle was behaving exactly as it had before the transmission was installed. This is the call we all hate to receive.

When he returned the truck for us to inspect, he stated that when he first started it up in the morning the OD light flashed very quickly and the vehicle did not have any power. The next morning was really cold and ideal for duplicating the customer’s concern. When I started the truck, I verified the customer’s concern as the OD light was blinking rapidly and the transmission was in failsafe. I noticed that the OD light seemed to be abnormally dim, but by the time I got the truck into the bay and hooked up the scan tool the OD light had stopped blinking. I scanned for codes and found none, and truck was no longer in fail-safe mode and seemed to drive normally at that point. So what changed? I did not move anything and didn’t even open the hood, so how did it fix itself? This was puzzling.

Once again I left the truck outside in the cold for several hours until the problem reoccurred, and when I hooked up the scanner I discovered that the scan tool had no communication with the TCM (Figure 1). Communication was okay with the ECM and ABS modules, but not the TCM. I proceeded to check the power and grounds to the TCM, and all connections and wiring seemed to be in order. By the time I got done with these checks, I realized that the TCM was communicating again with no codes stored.

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Figure 1

The only solid lead that I had was that I could always reproduce the issue when the vehicle was cold, and the TCM had no communication which seemed to be at the heart of the problem. Focusing on the TCM itself, I removed the module from the truck and placed it into the freezer, leaving the truck inside our warm shop. After a couple of hours, I retrieved the TCM from the freezer and reinstalled it into the truck, and voilà! The OD light was dimly blinking and the TCM had no communication with the scan tool.

To speed up the process and test the theory, I grabbed my heat gun and started warming up the TCM (Figure 2) and fairly quickly regained communication with the TCM.

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Figure 2

It also had a P1605 code in the ECM (Figure 3). I repeated this testing sequence again just to make certain that this was indeed the problem, and sure enough, got the exact same results.

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Figure 3

A new TCM for this vehicle is a 2000 model year-only application and was priced at more than $500.00. Since I had never replaced a TCM for this application and none of our other 14 locations had either, I figured that a used TCM would be a fairly safe bet and picked one up at a local salvage yard for $75.00. I installed the used part and everything worked as it should. Just to be on the safe side, I took the used TCM and dropped that in the freezer also and it worked even when frozen. We returned the truck to the happy customer a couple of months ago, and the vehicle owner reports that all is well.

In the end, the experience was a very unusual one. The decision to replace the transmission was in part due to the fluid condition, but the root of the problem came down to intermittent TCM operation caused by cold temperature conditions. The key to solving these types of issues is to remain persistent and find the common links to the problem. If you can isolate the clues to a handful of repeatable conditions, it won’t be long before you solve the problem and win the customer.

Remember To Update Those Tuners

By Chris Adams, Diagnostician

adams-chris-2Chris 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 is also holds ASE Master and L1 certifications.

We all know how important it is to make sure that the vehicles that come into your shop have the latest software loaded into the vehicle’s computer systems. No matter the make or model, they almost all have some kind of updated calibration that the OE decided was important enough for them to get the calibration approved and released, whether it be for drivability, fuel mileage, durability or just a software bug.

I have been reprogramming automotive computers since 2006 and have seen hundreds of actual fixes from software updates, while others are more “behind the scenes”. In those cases you might not really notice anything remarkable after the update, but this doesn’t necessarily make them any less important than one in which you can actually see or feel a change in operation. While reprogramming ECUs is not the focus of this article, it’s an important introduction to the prime subject: tuners!

Diesel tuners of the “programmer” or “downloader” variety where you actually plug into the vehicles OBD2 port and reprogram the ECM/PCM or TCM have some of the same issues that the OEM must deal with. Since most third-party calibrations are based on a factory, OE calibration, the modified version is susceptible to the same issues that can arise with the OE calibration, such as drivability, bugs, durability, or maybe power output that was not as advertised, etc. Any of these issues can result in an updated calibration from the tuner manufacturer. This is where it gets even more complicated, as the OE generally issues a TSB that alerts you that there is a re-flash available, or there is some kind of way to look up the calibration that is loaded in the vehicle and see if there is one more current.

In the aftermarket, this same information is not readily available and you won’t know if there is a update to the tuner until you install the updating software and plug in the device. It will then compare the files loaded on the tuner to the most current files that are available from the tuner manufacturer and inform you if there is an update, or not. I will tell you that in my experience, most owners will install the tuner and forget it. If I had to put a number on it I would say that 85-90% of all the tuners I have checked for updates were NOT current.

All of the software to update the tuners is available free of charge to download and install. I have not come across one that there was a fee to do so. Doing this will accomplish a couple things: Firstly, you have assurance that all the software on the vehicle is current, and secondly, add additional revenue for the shop. We usually charge at least an hour at our diagnostic labor rate to load the tuner with the latest updates in addition to the actual charge for reprogramming. The only “hardware” you need is usually in the box with the tuner, and if not, the items are readily available as most are a USB to micro USB cable, a USB printer cable, or a micro SD card to USB adapter. These items cover just about every tuner out there.

It’s always a good idea to refer to the instructions from the tuner manufacturer for specific procedures. A general rule of thumb that I follow is to uninstall the tuner from vehicle, reprogram the vehicle’s ECM/TCM with the latest available OE calibration (whether you are using a factory tool or a J2534 interface), update the tuner, then reinstall the tuner back into the vehicle. The first step is very important to uninstall the tuner, as this will “unlock” or “un-marry” the tuner from the vehicle. Not doing so can lock the tuner to where it can’t be reinstalled until unlocked again, and there is usually a charge from the manufacturer for this. Finally, hook up a line pressure gauge to the unit when you go for a test drive! A large majority of the tuner-related problems that I have seen involve improper line pressure, either too high, too low, or a slow response in line rise. These will create shifting issues and/or premature failure of the transmission, if not addressed.

I have included links where you can find the updating software to some of the more popular units:

http://www.sctflash.com/support

https://hsperformance.com/update-instructions/

http://www.bullydog.com/support

http://edgeproducts.com/updates/

http://superchips.com/updates/

http://www.hypertech-inc.com/support-update-software.aspx

http://www.madselectronics.com/download.html

http://www.bankspower.com/downloads

Here is a real-life example of why this process is important. A 2009 Dodge Ram 2500 6.7L diesel with a 68RFE transmission came into one of our locations with some shifting issues. This was a modified truck with the EGR/DPF deleted (very common modification), bigger injectors and an H&S Mini Maxx tuner. This particular tuner has optional transmission tuning software that is available for an additional charge. Under the “settings menu”, this truck had the transmission tuning displayed as “unlocked”, so I knew that the tuner was in fact installed with this option.

I wanted to eliminate the tuner from the equation, so I uninstalled the tuner from the truck (when you do this the tuner will reinstall the calibration that it saved when the tuner was originally installed) and continued on with the evaluation. Uninstalling the tuner did not fix the problem, but I did notice something pretty strange with the data from the scan tool:

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Figure 1

While under a load from 60-80 mph, the actual line pressure was correct but the desired line pressure goes as high as 220 psi. Since OE programming only commands a maximum of 160 psi in forward gears, the displayed desired 220 psi is obviously incorrect. I did verify with a pressure gauge that the actual sensor reading was correct and also tested with two different scan tools. The truck was not setting any low pressure codes, and uninstalling the tuner should have returned the vehicle to stock. What I was seeing did not match what I have seen in countless other trucks with the same drive-train, but why?

I went through the process of installing and uninstalling the tuner again with the same results, and looking on the Chrysler Tech Authority website I found a PDF file that you can download and save to search for calibration updates. The calibration in this truck showed as being current, so at this point I had no other choice but to force reprogramming with the same calibration number into the TCM (I say “force” because the system typically won’t reprogram if it detects that the loaded calibration is current, as this was). I used the Chrysler WiTech scan tool to do this, and after using the factory tool to reprogram the TCM, you see the new results here:

remember-to-update-those-tuners-1

Figure 2

You can see that the actual and the desired line pressure parameters now match each other. I concluded that using the tuner to “return vehicle to stock” did not reinstall the original calibration in its entirety and there was a residual effect on the factory line pressure table.

This particular tuner calibration had been updated multiple times, and one of the modifications they had done had altered the line pressure table. Here is a quote from H&S: Low Boost Fueling Option – This was added as an attempt to mock the feel of the old Pedal Response option that was omitted due to trans line pressure rise issues when we used that option.” The subject truck ultimately had an OD clutch failure. Can I 100% prove that a tuner that was not updated caused the failure? Not really, but when an update is released to fix a line pressure rise problem I think it’s a good possibility that had a negative effect.

In summary, it’s always important to ensure that all of the updateable software is current on the vehicle, regardless if OE or aftermarket tuning is installed. Diesel owners commonly go for use of tuners in conjunction with engine component adds/deletes to get the maximum performance out of their trucks. The OEMs are wise to this practice and make it difficult for third-party tuners to alter some of the calibration parameters. Incorrect line rise is the prime killer for transmissions working under these conditions, so ensuring it’s correct is in everyone’s best interest.

Diagnose using application charts

By Barry Bartlett, Diagnostician

bartlett-barryBarry has over 45 years of automotive experience. He has done everything from managing, owning, and operating his own general repair facility to working in the transmission industry. He’s a ASE Master tech. with L1 advanced level diagnostics, the highest level of certification available. Barry and his wife Janet have been married 42 years and are proud parents of 6 children and 26 grandchildren.

One of the best and easiest diagnostic tools that I use almost daily for diagnosing transmission problems is pass book or application chart information. When I have a shifting issue, a review of what solenoids and friction elements are applied in each gear can let me see what areas of the transmission the problem may be caused by, so I can then differentiate whether there is an electrical or mechanical issue causing the symptoms.

diagnose-using-application-charts

I will use the 4L60E transmission for the following scenarios (refer to FIG. 1):

Third Gear Neutralization

If the vehicle is shifting to first and second gear and feels like it neutrals when third is commanded, a review of the solenoids shows that both are on for first gear, so I know that both are turning on. When second gear is commanded, SSA turns off. In third gear both solenoids are off, so when I feel the neutral condition, it is a good sign that SSB is turning off so I can then conclude that both solenoids are working properly.

Testing further, I know that on the shift from second to third gear that the 2-4 band turns off and the 3-4 clutch applies. Next, I shift to manual second while increasing the vehicle speed until about 40mph, then shift to overdrive and let off the gas. If I have a second gear ratio when fourth gear is commanded, it will reveal the cause: the 3-4 clutch is not holding. Referring to the chart, I see that the 2-4 band applies at this point. If the 3-4 clutch does not hold, the transmission remains in second gear because the forward clutch and the 2-4 band are holding, thus indicating that the 3-4 clutch is not.

No Movement from Stop

If I have no movement from a stop I can test to see whether the forward clutch is bad, or if the forward sprag clutch is not holding, by shifting into manual low. If there is now movement, the forward sprag is bad because the overrunning clutch holds the sprag, but if it still does not move then it is the forward clutch causing the concern.

No Second or Fourth Gears

If I am missing second and fourth gears but all other gears are ok, the cause points to the 2-4 band not applying. Many times I have had customers complain that their transmission stays in first gear for a long time before it finally shifts, and some will report that they have to let off the gas pedal in order to get it to shift. They might think that it is then in second gear, but they are actually in third gear and may not notice that there is no upshift into fourth gear.

Remember that in first gear both shift solenoids are on and in third gear, both are off. That would indicate that the solenoids are working ok and point to a friction element, and as the chart shows, the common element applied in second and fourth gears is the 2-4 band. The 2-4 band holds the sun shell. Sometimes the sun gear will break away from the sun shell on the 4L60E units and you will lose second, fourth, and reverse gears which then require the replacement of the sun shell.

Forwards but No Reverse

What if I have all forward gears but no reverse? A look at the application chart shows that the reverse input clutch and the low/rev clutch engage to engage reverse gear. An easy way to test this is to accelerate to about 20mph and pull it into manual low to see if you have engine braking when you let off the gas. If engine braking is working, that indicates that the low/rev clutch is correctly holding the sprag clutch from overrunning. This would indicate that the reverse input clutch is the cause. If you do not have engine braking, it points to the low/rev clutch being bad and preventing reverse. It is good to confirm the integrity of a sprag clutch before performing a rebuild, because you may not be able to tell when the transmission is disassembled and you are holding it in your hand.

In addition, the chart can be helpful if you suspect a component problem. For example, a review of the solenoid application chart will show the outcome if shift solenoid A (SSA) is not turning on: second gear starts and the transmission will shift into third, but if SSA is not turning on you will also have no fourth gear. Second and third gears would be the only forward gears that function.

If shift solenoid B (SSB) is not turning on, the solenoid chart shows that the transmission would have fourth gear starts, and manual second and third gears at about 30mph. When shifting up from manual second to third or overdrive gear, I will have fourth gear when the computer commands because the SSA is working.

What is the effect if there is no power to any of the solenoids? We would have third gear with no upshift or downshift when in drive. Manual second would function because it is hydraulically shifted into second gear without solenoids, but in drive or overdrive we would have only third gear because no solenoids are turned functioning. I can look then know to look for electrical/control problems.

When there is no power to the solenoids it will generally set multiple solenoid codes on any transmission, so check fuses and ensure there is power through them, then check for power at the transmission connector. If no power at the fuse you could have an ignition switch problem (common on Chevrolet), but if no power at the transmission fuse, check your power distribution to identify where the power is sourced to the fuse.

On most GM trucks and cars you can actuate the solenoids with a scan tool and listen for the solenoid to click (both solenoids can be tested in this manner) and let you know that they are working and that the computer has the capability of turning them on and off.

Some vehicles will shut off power to the transmission when it has a code set by turning off the relay that supplies power to the transmission, so be sure to look for codes that could be causing a limp-mode condition. This is commonly seen on 604 Chrysler transmissions, where in limp mode it will shut off the relay leaving reverse and second gear only. Look for codes and see if there is a speed sensor, pressure switch problem, or some other issue causing the limp-mode condition.

It is also a good idea to monitor the status of the solenoids for the proper gear, because I have had defective computers give false information showing that they are calling for a certain gear on the scan tool, but yet not turning on the solenoids that are needed for that gear. I often tap into the wires with lab scope, voltmeter or test lights to make sure that the computer is turning on and off at the correct time.

Many transmissions now use pulse width modulated solenoids so instead of on and off  the chart may show high and low pressure and/or high or low amperage. Also you might see on the application chart “N.O.” which stands for “normally open”, and “N.C.” which stands for “normally closed.”

There are several sources to obtain the Passbooks and charts referenced in this article. Collecting application charts and saving them for future reference can help with the diagnosis of any transmission, and can make your recommendation for repairs much easier. As you become acquainted with and review application charts, you will find diagnosing transmission shift issues easier and quicker to pinpoint.

Common Symptom, Uncommon Cause: Shorted Sensor Defeats Electronic Controls

By Dan Frazier, Diagnostician

frazier-danDan has been in the automotive industry over thirty years and is an ASE Certified Master Technician. Dan has a college background in electronics engineering and specializes in diagnostics and computer controls.

The subject of this article is a 2006 Hyundai Sonata that came into our shop with a no-shift complaint. It was likely in limp-in mode, so in order to get down to the cause of the problem I began with a cursory preliminary inspection.

My initial inspection revealed several obvious issues: the MIL didn’t self-check, no communication with the PCM/TCM unit, airbag light on, and an oddly flashing cruise lamp. A short road-test confirmed the no-shift condition. After getting some diagnostic time approved from the customer, I began my in-depth diagnosis.

Whenever I’m faced with a communication issue, usually the first place I go is verifying power, ground, input and output to the offending modules. A good place to start is checking communication lines at the DLC and checking fuses. And I mean ALL of the fuses. Not that I’ve ever had a “D’oh!” moment after 30 minutes of checking things, but it happens to the best of us. I quickly found a blown fuse that was labeled B/U lamps. Replacing it blew the new fuse immediately, so I knew I needed to look there first.

Looking at a power distribution diagram showed that fuse powering the B/U lamp circuit also powers what Hyundai calls pulse generators ‘A’ and ‘B’, or more commonly known as transmission input and output speed sensors. In addition, the transaxle range switch and the vehicle speed sensor are also powered through this fuse. All of these components are easily accessible on the top of the transmission, and it didn’t take long to find the connector to the pulse generator melted:

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Figure 1

The pulse generator sensor is a hall-effect sensor with a power and ground, and the output feeds the K-line, or low speed communication circuit.

Here’s where the fun began. The vehicle speed sensor on the transmission doesn’t supply vehicle speed data directly to the PCM. It sends data via the K-line to the BCM, TPMS, ABS, and traction control modules. Vehicle speed input to the PCM comes from the RF wheel speed sensor, which is basically an ABS sensor, even though the vehicle doesn’t have ABS. This is a rather odd, but common, setup on Hyundai/Kia vehicles. Side note: if you run across one that has an erratic wheel speed sensor signal due to a cracked tone ring, the rings are available separately from the dealer, are very inexpensive and usually on the shelf.

The K-line also supplies scan tool communication. When the sensor and connector melted in this case, it grounded the K-line circuit and therefore, no communication. Once I snipped the connector off, communication was restored and I was able to scan for codes. The only code that showed up was a P0700, general transmission fault. I didn’t have a code for the pulse generator because it wasn’t an input to the PCM/TCM. I still didn’t have any communication with the TCM, nor did I have a check engine light or a code for the MIL circuit. Time to dig a little deeper into the problem.

One thing I like about Hyundai/Kia vehicles is that for the most part, they’re pretty easy to work on. Also, their electronics seem to be pretty reliable, as is the case with most of their Asian counterparts. They don’t seem to have very many intermittent issues like some domestic manufacturers (think TIPM!) and their components are usually either dead or alive.

The PCM/TCM units on this model are next to the air cleaner with the connectors facing up, which makes back-probing circuits a breeze. In about 5 minutes I had the instrument cluster out and knee bolster removed in order to provide access to the fuse/central junction block. I now had easy access to test just about any circuit on the vehicle. With the cluster out, it didn’t take long to diagnose the cause of the MIL issue; you can’t light up what isn’t there. The socket and bulb was missing from the back of the cluster:

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Figure 2

These bulbs are not sold separately from the dealer; you have to buy the whole cluster. Moving forward with diagnosis, it didn’t take long to verify powers, grounds and data lines to the PCM/TCM, and they all tested okay. The TCM side of the PCM/TCM unit itself was apparently dead.

The hardest part of this diagnosis so far was finding complete information within the wiring diagrams and service information. The pulse generator in the transmission only appears in the power distribution and computer data line schematics; if I hadn’t already known its function, I would have had a very hard time finding it and description and operation of that component is virtually non-existent. The pin and wiring assignment for the DLC is backwards (like a mirror image) and some of the pin assignments and wire colors at the PCM were wrong. This seems to be a somewhat common issue. If you’ve spent much time looking at the O.E. service information, you would know it can range from very frustrating to downright hilarious. If you see something that looks wrong, it very well may be. Double-check it against another source – it does happen more than infrequently.

The used car lot that brought us this jewel was a pretty good customer, but had a reputation for wanting to fix the bare minimum as most car lots do. As expected, all he wanted to do was make it shift. In fact, he showed up just before closing time with a used PCM/TCM unit in his hand. Installing a used module is usually a crapshoot – I don’t recommend it – but we told him we would give it a try. We ordered a speed sensor, but finding a connector pigtail was a different story. Hyundai/Kia, like Nissan and a few other OEMs, don’t offer connector repair replacements. You would have to buy the whole harness, kind of like the bulb in the cluster. I have sourced those bulbs in the aftermarket before, but wiring pigtails are slim pickings. We ended up having to send one of our guys to a salvage yard to clip one off of a donor vehicle, and charged accordingly for it.

After our parts arrived and were installed, the Sonata shifted normally, but did set a code – P0630 – for VIN programming error. You would’ve never known it because of the missing check engine light bulb. We possibly could have resolved that issue with a reprogram of the PCM, but as expected, the customer didn’t want to spend any more money than necessary to get it rolling. It was somewhat of a challenge getting through the service information, but turned out to be a fairly easy and profitable job.

The shorted pulse generator created a situation that damaged the TCM electronics, and the vehicle was tampered with to hide the issue. Auction cars are often technical throwaways that somebody didn’t want to deal with. You have to expect the unexpected. A little research and detective work go a long way in these cases.

The Case of the Output Speed Sensor Spike

By Dana Deeke, Diagnostician

deeke-danaDana joined Certified Transmission in 1991. Dana has worked in all positions at the Lincoln location, starting as an R&R technician and is now our current diagnostician for our Lincoln, NE facility. He enjoys car racing and spending time with family and friends.

Occasionally you will have a vehicle come into your shop that takes you down a different path than what you might have expected. The following account tells the story of one of the times that it happened to me. The star of this show is a 2006 Chevrolet Silverado 2500 4×4, equipped with a Duramax diesel engine and an Allison transmission.

The information on the checkout sheet stated that the customer had a concern of truck being sluggish from a stop and slipping or no 6th gear. The customer also stated that the transmission had been replaced approximately 30,000 miles prior to his visit. The truck had been to another shop previously and the customer was told that the transmission was failing.

Armed with an understanding of the customer’s concerns, I started the diagnostic process like I always do by hooking up the scan tool and checking for any trouble codes. The code check revealed P0729 and P0733. P0729 shows up as a ratio error in 6th gear, and the P0733 is 3rd gear ratio error. A quick check of the fluid indicated that it was full, red, and had no burnt odor. I took the truck out for a road test with the codes in memory, and much to my dismay, the truck functioned properly and nothing on the data stream appeared out of the ordinary, including the output speed sensor signal.

Next I decided to clear the codes and drive it with a graph on the input speed, output speed and current gear. The truck shifted through all the ranges properly, and the speed sensor graph looked clean and smooth and no codes were set:

Figure 1

Figure 1

Somewhat frustrated, I pulled into a parking lot and looked through some of the other PIDs hoping to see something unusual. Upon pulling into the parking lot, I did not put the truck in park, instead simply idling in drive. The next step was the first in finding the problem. Like most techs, I am always trying to listen and feel what is going on with a vehicle. As I sat there I thought I’d heard a slight exhaust leak, and I would want to note it on the paper work if there was one. I decided to power brake the truck a bit to see if I could hear where the leak might be coming from, and that’s when I saw it: a momentary spike on the output speed sensor graph, and even better yet, I was able to make it happen fairly regularly. During this screenshot the truck remained completely stationary:

Figure 2

Figure 2

Now the question that needed answered was what was causing it? I noticed that the spike in the output speed signal would happen whenever the input speed signal increased. My first thought was, is there voltage that is being induced into the output speed sensor circuit? Once I was back at the shop I pulled up a wiring diagram of the transmission circuit and I also wanted to see what the routing of the input and output speed sensors wires looked like.

Looking at the wiring on the truck itself, I couldn’t see any routing issues and testing did not show any signal transfer from the input sensor. While I was looking things over, I checked chassis grounds and even removed the serpentine belt to make sure there was not any static charge that may have been causing voltage problems. Removing the belt did not have any effect on my concern. I thought about some of the Chrysler vehicles I had seen with excessive alternator ripple causing phantom voltage in the output speed sensor signal. Though I had never seen this on this type of vehicle, I decided to run an alternator charging output and ripple test, and everything passed with flying colors.

With the help of an assistant, we unplugged the output speed sensor from the transfer case and did the power brake test again. As expected, I could not get the output speed sensor to spike. Next, we plugged the sensor back in and did the power brake test again and it confirmed that the spike returned. Next we removed the sensor but this time we left it plugged in, again did the power brake, no spike occurred. So the sensor had to be in the transfer case for the symptom to happen. Based on what we were seeing (and not seeing), it was determined that the transfer case itself was the culprit.

This truck had a lot of miles on it and as far as we could tell it had never had a transfer case replacement. There was enough wear inside to allow the output shaft to move around when the torque of the diesel was applied causing a false output signal to be generated.

At the beginning of the testing, the symptoms and data appeared to point to something electrical causing the problems, but in the end it was a purely mechanical issue; one that was not related to the transmission at all. We installed a remanufactured transfer case, did multiple road tests, and confirmed that the symptom had been corrected. The customer was happy that his “transmission” problem had been corrected.

As demonstrated here, the symptoms don’t always lead you down the right path. In many cases you will need to leave the familiar path and go down the road less traveled. If not for the spike being witnessed during the testing, this issue may have been impossible to find. Always watch for clues and don’t ignore the unusual. Sometimes we have to be more of a detective, rather than a tech.

Surges in a 2006 Chevrolet Impala

By Chris Adams, Lead Diagnostician

adams-chris-2Chris Adams started with Certified in 1986 as an R&R technician. He has an Associate Degree in Automotive Technology from SCC in Milford, NE. He also holds the ASE master tech with the L1 certification. Currently he is our diagnostic trainer and is responsible for keeping our diagnostic techs at the retail locations at the top of their field, and keeping current with all the latest trends and tools in our industry. Chris also works closely with the technical dept at the remanufacturing plant and helps coordinate our fleet of research and development vehicles for testing.

Recently a 2006 Chevrolet Impala came into one of our retail locations with a surge complaint while cruising on the highway between 60-65 mph. I drove the vehicle with the customer to verify the concern and was able to duplicate the circumstances in which the vehicle acted up. While watching the tachometer I noted that there was a noticeable 150-200 rpm surge while TCC was applied. It felt like a typical TCC surge as a result from a leak in the TCC regulator circuit, so additional diagnostic steps were in order. We discussed this with the customer, and he authorized the additional time. At this point I was fairly convinced that we were going to need to go inside the unit.

We always start our evaluation with some pretty basic steps: check fluid level and condition, scan for codes, perform a battery and charging system test, and an undercar inspection. At this point everything was looking good, fluid was full and clean, there were no DTCs for the engine or transmission, and the battery and charging system test results came back error-free, and there were no obvious problems shown with the visual inspection.

At this point we proceeded to take the vehicle out for a road test with the scan tool connected so that I could monitor the PIDS for the TCC command while looking at the TCC duty-cycle while the surge was occurring. It appeared that the PCM was commanding the change, although it was very erratic. Given this information, I now had to try to figure out what PCM inputs could be causing this to happen.

After a few considerations, I turned my attention to the TPS signal. Utilizing a Snap-On Verus Pro scan tool there is a PID called, “CALC TPS %” and while monitoring this value, I saw what was making the PCM vary the duty-cycle and therefore causing the TCC surge. There was a noticeable jump in the TPS signal when the surge was happening (Figure 1). As this is a “drive by wire” system, I also looked at the APP signal and it was smooth. Further testing was now in order.

surges-in-a-2006-chevrolet-impala-0

Figure 1

After looking over the circuit wiring diagram and connector view from GM Service Information, and also checking for pertinent TSBs, I hooked up the scope right at the throttle body to TPS1 and TPS2. At a throttle position just a little off idle, I could see the glitch in the signal in both of the inputs (Figure 2). After verifying there were no ground issues I was leaning toward recommending that the throttle body be replaced. One last thing I needed to check was if there were any updates to the PCM calibration. Checking the current calibration against the GM TDS website, I noted that there were several updates to the calibration, although none of them relative toward the issue that I was having.

Figure 2

Figure 2

My recommendations for repair included a pan inspection & fluid/filter change, a replacement AC Delco throttle body, and reprogramming of the PCM. All repairs were authorized by the customer and we proceeded with the repair. After my recommended repairs, drivability was normal, data signals were smooth, and the TCC surge was gone. The vehicle was then returned to the customer. Another one done, or so I thought.

Unfortunately, two days after the vehicle was returned to the customer, he returned with the dreaded, “It’s still doing the same thing.” I grabbed the scan tool and went for a ride with him, and this time it took quite a while for him to get the vehicle to act up and it was not a repeated surge like it was before. However, under just the right set of circumstances you could see the tach rise up by about 50 RPM. This little RPM flare would only happen at very light loads. While I could see the duty-cycle command change when this happened (Figure 3), I could find no reason for why it happened as the TPS signal was smooth.

Figure 3

Figure 3

I then recorded all the transmission data so I could go back and look at it more in depth, to no avail. We again went for another road test while I was looking at the engine side of the data and happened to catch something changing when the RPM flare occurred. This particular vehicle has the “DOD System” (Displacement On Demand) where under light load conditions it can deactivate cylinders 1 and 7 on the left bank and cylinders 4 and 6 on the right bank at cruising speed. On the scan tool there is a PID called, “Cyl deact system command” that will either show V8 or V4 and this is where I saw the change: every time that the PCM commanded a change in state from either 8Cyl mode to 4Cyl mode or vice versa there was a quick dip in the TCC duty-cycle command (Figure 3).

It was more noticeable from V8 to V4 because of the light load, when going from V4 to V8 there was an increase in load that triggers the change in state and the small flare was not as noticeable. After verifying operation on another like vehicle, I have to conclude that this is a normal operation and just a byproduct of the change in state from V8 to V4 mode and probably programmed into the software to make sure the transition is smooth so the owners do not notice a bump or jerk during this transition. Since I am not a GM engineer, this last statement is just my opinion. I have never seen anything in print to 100% verify.

Less Time Spent Diagnosing

By Richard Middleton, Diagnostician

middleton-richardRichard Middleton was a diagnostician at our Grandview, MO retail store.

Recently, we sold a 4L60E to a neighboring shop. They installed it, but then they brought it back to us due to a P0753 shift solenoid A code. It would reoccur consistently and almost immediately when driving. However, the transmission would NOT go to failsafe mode (this is a key point).

I did a quick resistance check on the solenoid and it was fine, so I thought maybe it was a connection issue.  I wanted to do some amp tests with a scope and amp clamp but I found it difficult to get to the circuit without opening the harness (which was far too much work).  So, I just did the amp test at the transmission with a test harness plugged in. It was fine at 0.4 amps on the A solenoid.  I checked the B solenoid for comparison and it was 0.4 also.  This test is dandy but doesn’t show you a problem with the wiring, connections or computer.

The best test would have been to drive it, measuring amps on the A solenoid wire between the solenoid and the computer, but since I couldn’t find easy access to the harness, I decided against it.

less-time-spent-diagnosing-0It is possible to jumper across the fuse that powers the solenoid (above) with a wire and put your amp clamp around that; unfortunately, there are other devices on the fuse that activate while driving. They draw extra current and create inaccurate readings. But, if you do the readings in the bay using bi-directional controls with the scan tool, the other stuff on the fuse isn’t active.  This is the way I chose to do it.

less-time-spent-diagnosing-1I measured amperage at the fuse while turning the solenoid on using bi-directional controls in the scan tool (above).  This loads the entire solenoid circuit just as the computer does running down the road.  This test was showing 0.4 amps on both solenoids, so I was pretty sure it was a computer problem.   I called up the shop that installed the transmission and they said, “yes, the code was there before”.  This would have been nice to know upfront, but ok…

At this point, I knew the computer was capable of making correct amps and the solenoid, wiring and connections were all fine. The code was triggering but without tripping the failsafe.  It was looking like a bad computer, probably in the section that makes the decision whether or not to trigger the code.  Usually a computer failure that creates a solenoid code would be in the amp driver.  But since this transmission continued to work even after the code triggered and the computer could flow correct amperage in the bi-directional test, this makes it a logical decision to try a complete computer replacement.

After installing a new computer, quickly reflashing the system and completing a not-so-quick 30 minute anti-theft relearn, the problem was fixed.  So, with very little time invested in the diagnosis this car was fixed.  I spent more time thinking about it, worrying about misdiagnosis than actually testing it.

Beware Antifreeze Contamination From Nissan Radiators

By Jerry Tipton, Diagnostician

tipton-jerryJerry has been in the transmission industry for more than 25 years, with experience in diagnosing, rebuilding and installation of many types of transmissions. He has a degree in automotive technology from SCC Milford and also has attended many automotive seminars and classes. He is also an ASE Master tech.

By now, everyone in the automotive industry should be aware of the infamous Nissan radiator issues that cause antifreeze to contaminate the transmission oil (and vice versa). If you’re not, you should research the topic as the implications are many. This issue isn’t as easy to detect as it was several years ago. Today’s transmission fluid doesn’t always tend to froth up into the “pink milkshake” that was always a telltale sign of contamination. Small amounts of glycol can wreak havoc on the transmission, and many times a test kit is required to detect it. I know this is nothing new, but perhaps a refresher with a few new things that you may have not previously considered. The vehicles I will be referencing will be a 2005 Nissan Pathfinder 4×4 and a 2007 Nissan Pathfinder that had related issues all within the last six months.

The 2005 Nissan Pathfinder case started as a carry-out transmission installed by a wholesale customer. This vehicle came back to the shop with a torque converter shudder after being driven less than 2K miles. We started with a standard preliminary evaluation and the visual inspection revealed that there was transmission fluid in the coolant as evidenced by the “purple milkshake” in the reservoir. We also found some transmission fluid in the radiator that had been previously replaced along with the transmission. This was alarming, but to prove it a sample of the transmission fluid was captured for testing.

The fluid test exhibited trace contamination of ethylene glycol in the transmission fluid. After repairing the transmission damage, pulling the radiator to have it pressure tested was in order. The radiator tested out ok, so this case was even more perplexing. Our first thought was that the original installer didn’t flush the lines or auxiliary cooler when the transmission was replaced. At this point we felt that flushing the cooler lines and auxiliary cooler should take care of the remainder of the vehicle issues. This also required flushing of the engine cooling system to clean out the transmission fluid.

After completing the road test and with everything working properly, we took a sample of fluid to run a test for ethylene glycol only to again find trace amounts of glycol in the fluid! How could this be? After some head scratching we determined that the auxiliary cooler had small amounts of anti-freeze trapped in it that flushing apparently didn’t force out of it. Now that we were aware of this issue, the next step was to replace the auxiliary cooler and road-test again. This completed the repair. It is hard to understand why the auxiliary cooler wouldn’t clear with the flush machine that we use, but because of this discovery, it is now standard procedure for us to replace the radiator and the auxiliary cooler on these vehicles when replacing the transmission.

Figure 1

Figure 1

The next case was a 2007 Nissan Pathfinder. This one arrived with coolant in the transmission, and transmission fluid in the coolant. After going through the same steps of transmission replacement as the previous case, replacing the radiator and auxiliary cooler, then flushing cooler lines and engine cooling system, you would think that all the bases would be covered, right? Nope. It would seem that the rubber components in the cooling system do not play well with transmission fluid! As if.

There were additional clues that this one seemed to have been contaminated for a longer period of time, as evidenced by very soft radiator hoses. After the radiator hoses were replaced, we figured that we’d found the last of the glycol issues. Alas, the problems continued. The darn engine was running hot. We had a new radiator and the fan was working, so the next step was to take a look at the thermostat.

Well, well, well. The rubber swelled to a point partially restricting the flow of coolant to the engine.

Figure 2

Figure 2

Now this begs the basic question: where does it end? Clearly every gasket and seal in the cooling system is now suspect to failure. How do you convey this to a customer so that they can understand? Facing increased repair time, labor, and parts becomes a hard sell. It’s always in the best interest of the customer to sell them what they need in order to prevent a future failure. Sometimes they can’t see beyond what is broken “right now”, so it’s our job to thoroughly explain these issues to them until they’re confident in paying you what it takes to accomplish this.

These cases illuminate a need to think about the full scope of damage that could be incurred by a related system failure when they interact with each other. While not necessarily common, it’s the extra thought and perseverance that keeps customers coming back to your shop. “Fix it right the first time” is something to live by. Learning what to watch for is half the battle, as shown here.

Once Again: Check Those Grounds

By John Griffin, Diagnostician

griffin-johnJohn is a Diagnostician for Transmissions Incorporated, a division of Certified Transmission. He has been a valued member of our team since 1990. When not at work, John enjoys working on old cars, fishing, and racing sport compact cars with his family.

However, one thing that has remained fairly constant through the years is the wiring that connects to all of those “magic boxes”. Copper wires in a vinyl sheath; seems simple enough. Where it gets a little complicated is with CAN network protocols, module connectivity, and the like. It’s easy to suspect these things when diagnosing a customer issue, and just as easy to forget the basics. The following cases involve the latter: basic wiring issues creating a customer complaint.

A while back I had a call from a neighbor who was experiencing some shifting issues in his 1996 Ford F250 in which we had installed a remanufactured transmission into a year ago. He told me it was kicking in and out of gear on the highway. I made plans to go for a ride with him after I got off work. When I arrived, I checked for codes and found none. The condition of the transmission fluid was good, and during a 20-mile ride it shifted great. He explained that it had acted up on his way home from work the night before. Based on his explanation, I told him that it could possibly be dropping in and out of torque converter lockup. We just needed to prove that theory.

Since the PIDs on the scanner looked good and there were no codes present, I told him we needed to clean the grounds first, and then see what happens. Since he has some mechanical ability, he said he would do that and let me know. A few days passed and he called to tell me that it was still having the same symptoms, but he noticed it only happened with the headlights on. Since he had to get to work, we made plans to drop the truck off at my house so I would drive it into the shop the next day.

As I drove the truck in the next morning, I was able to confirm the concern. He was exactly right: the truck only dropped in and out of converter lockup with the headlights on. Now that I knew we were on the right path, I now needed to find the root cause of the issue.

A quick inspection under the hood indicated that the battery cables were clean on both batteries and the grounds had been cleaned. Next, I checked the lights. I checked turn signals, marker lights and headlights on the front of the truck. While checking the rear lights I noticed that the right rear park light was dim as compared to the left rear. I ran a jumper wire from ground to the taillight and it brightened up. I then repaired the taillight ground, and after a test drive I knew the problem was fixed. The truck has been running great for six months now with no problems.

Correct taillight operation is crucial to the torque converter lockup circuit. Bad grounds, EMI, intermittent shorts and opens can all contribute to issues in that system. Simply checking battery grounds is not enough. Remember to check trailer wiring, also.

My second case involves a 1995 Chevy van, and came into the shop with the complaint of not shifting with the headlights on. The van has a 5.7 engine with a 4L60E transmission. The transmission fluid was correct and clean and there were no codes stored. My initial road test was with the lights off to see if the transmission operated correctly. The van shifted through all of the gears and went into lockup without a problem.

My next road test was with the headlights on. The van started off in first gear, but would not make the 1-2 shift. There were no codes set, and the 1-2 shift was not being commanded per PID data. My initial thought was a possible ground problem with the light circuit, so I printed out a wire schematic of the headlights and taillights to review. While under the hood of the van I noticed that someone had been in there previously, apparently repairing some type of an electrical problem. I noted that the van had a new battery, two new battery cables, and a new alternator.

While reviewing the wiring diagram, I located the headlight ground on the left side of the radiator support. There were three wires coming out of the wire loom bolted to the radiator support, and a frayed wire on an eyelet going nowhere. Looking at the new negative battery cable, I saw that there was an accessory ground pigtail with an unused splice connector attached to the end.

I removed the broken eyelet from the radiator support and then cleaned the accessory ground ends. I ran a new wire down from the negative battery cable to the radiator support ground, and then performed an electrical test to verify the starting and charging system were working properly from the previous repair. After road testing the van with the headlights on, I confirmed that the transmission was now shifting properly. The van was returned to the satisfied customer.

Each of these cases had its own cause: environmental exposure and age in the first case, and a careless DIY’er or tech in the second. Regardless of the cause, the cure was common to them. Grounds are easy to overlook; it takes a little more testing to prove that a ground is bad. However, they cannot be ignored, and in many cases, will fix those electrical gremlins that we love to chase.