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).


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).


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).


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.

Transfer Case Gets The Shaft

By Dana Deeke, Diagnostician

author9Dana joined with 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.

There are a lot of us in this industry that have been that have been at it for a long time, and I think most of us have said more than a few times, “Well that’s a new one.” I don’t know how many others of you out there have come across this problem before, but I know in my personal experience I have not. While this is not a terribly technical story, it is one that we found interesting, and as you will see, it had a scenario along the way that would make it a little more difficult to figure out.

What I am referring to occurred on a 2008 Chevrolet Trailblazer SS. This vehicle originally came into our shop with a concern of a leak between the transmission and transfer case. One thing to note: the transmission had recently been rebuilt by another shop, and the problem had started shortly after the work they had performed. As we all know, getting a good description of the concern and any information about previous work from the customer is very helpful. We are fortunate here that our service writers make this a priority, and it is a real time-saver in many situations.

As is standard procedure, once we have the concern and other pertinent information the vehicle is brought in for a visual inspection. In many cases when the vehicle has a leak concern or a vibration, I like to bring it in the shop and inspect it first before driving it. Sometimes the concern is an operational problem, and the customer either doesn’t know or doesn’t mention that it does leak. By bringing it in first, if it is leaking and it is not clear where it is coming from, I can clean it up at that point and drive it once rather than driving it first, finding out that it has a leak, then having to clean it up and drive it again to find the source. I can’t tell you how many times a vehicle has come in with a leak that was about to blow a cooler line off, or a vibration and the driveshaft was about to fall out.

There was fluid found hanging off the bottom of the transfer case where it mated up to the extension housing, but it was not the source of the leak. The transmission vent hose was routed above the transfer case and it was pretty easy to tell that fluid had come out of this vent onto the transfer case. My first thought was that transmission overheated and vented fluid. I scanned for codes thinking I may see an over temperature code, transmission component slip code, or something like that. No codes were in the system. At this point I had not yet done the most basic thing: check the fluid level and condition.

I checked the fluid and to my surprise it did not show any signs of overheating, but was overfilled. At this point I kind of assumed (we all know the saying) that the installing shop overfilled the transmission. When we do an inspection on the vehicle, we make it a point to check all the fluid levels, including engine oil. On this vehicle, when I checked the level of the transfer case I was surprised to find in was basically empty. We filled the transfer case up, removed the extra fluid in the transmission, cleaned up the fluid and went for a couple different extended road tests throughout the course of the day.

The vehicle sat overnight and in the morning we checked fluid levels again and found the same condition but on a smaller scale. Now most of us have come across the opposite problem, where the transmission is low and the transfer case is overfull, but on this vehicle we have the opposite problem. Could a failing transfer case input seal cause fluid transfer like this? It was time to get authorization to pull the transfer case and do some investigating.

After our technician removed the transfer case we inspected the input seal. It did not appear to be damaged as far as the rubber part looked and the spring was intact. We checked to see if the seal was correct for the application and it was. We inspected the housing that the seal is driven into and it looked acceptable also, so I didn’t know what to think. We decided to make sure that the vent on the transfer case, or any of the hoses going to it, were not blocked. They were all clear. Do we just try another input seal and see what happens?

As I mentioned before, this vehicle had been worked on recently, but we were not able to find out if the input seal had been changed at that time. We happened to have another GM transfer case sitting on the bench that had been replaced with a remanufactured one. It was not out of the same vehicle but was the same style. Scratching our heads and looking at the unit that had been previously replaced, we noticed that the “plug” that is at the bottom of the splines in the hole of the input looked like it was not positioned as far down in the splined hole of the input. (FIG 1). I know that one will be hard to see in the picture.


Figure 1

We did a quick measurement and found that the plug in the bottom of the hole was more than a quarter inch deeper in the hole, and further inspection showed a witness mark on it consistent with the size of the machined area of an output shaft, also hard to see in the picture. Next we decided to pull up an exploded view of the transfer case. (FIG 2). The “plug” (#6 in exploded view) we were looking at had bonded rubber on it and also acted as a seal.


Figure 2

Here is where the odd scenario that I referenced earlier comes into play. We contacted the customer and had them come down so we could show them what we had found, because we were not sure if there was any other damage to the internals of the transfer case, customer had driven it with no fluid in transfer case for an unknown number of miles, so we recommended installing a remanufactured one. The customer agreed, and we ordered the reman unit.
After returning from a test drive on another vehicle the installing technician called me over saying there was a problem. When he went to stab the transfer case onto the transmission it stopped before it would fully mate up to the transmission to transfer case adapter, it was bottoming out on the output shaft. We learned that this transmission when rebuilt by the other shop had been fitted with some performance upgrades including an aftermarket output shaft (FIG 3).


Figure 3

Now it was making sense. Upon measuring the length of the output shaft that was in the vehicle against one in a transmission we had on the bench, the one in the vehicle was longer. The theory we developed was that when the transfer case was installed after the transmission rebuild, the installing tech did not make sure it was installing flush and probably pulled it up with the bolts. This caused distorting of the seal and allowed fluid to actually pass from the transfer case to the transmission.

We talked to the guys that build the transfer cases and asked how the plug was installed, and they let us know that it is driven from the inside out. We asked if it could be driven in a bit so we could gain a little clearance between it and the output shaft. It sounded like we could carefully drive it back down, just enough to clear so the output shaft could not damage it. We double checked our measurements and installed it.

I wanted to put a few miles on this vehicle at this point, and since it was at the end of the week we also let it sit over the weekend. The next week everything looked ok and the vehicle was delivered. After a couple weeks of driving and rechecking it, everything was as it should be and the vehicle has been out on the road for several months now.

We are happy that the installing technician alerted us to the problem and really helped to point us in the right direction. Your installing techs are a very valuable part of your team; I think sometimes we forget that. In this case, paying attention to the basics helped to solve what we felt was a pretty unusual problem.

Attention To Details Solves Phantom Voltage Code

By Mike Greer, Diagnostician

author10Mike 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.





A growing trend that we have been seeing at all of our repair shop locations involve vehicles that are brought to us when a customer is referred to us by a general repair facility, or brought to us directly by the repair facility for diagnosis. In all cases, the shops are convinced that the vehicle either needs a transmission replacement, or that they feel the vehicle symptoms indicate a problem with the transmission. We have all seen it before when a vehicle shows up with engine misfire that is perceived to be the transmission, or a locked up fan clutch that is making the transmission “slip” or not shift into the higher gears. These types of issues are not going away any time soon, and actually things are getting to be more common as vehicle systems increasingly become more integrated and dependent upon each other to make the whole vehicle work the way it was designed to.

The subject of this article is a 2007 Nissan Maxima that was brought to us from a shop that we do a lot of work with. They had initially called and wanted to see if we could point them in a direction on what to look at. The shop had stated the vehicle had code P0868 (secondary pressure down), but after the code was cleared, it had not returned yet the car was still acting up. It would cut out and go into limp mode. I had asked about any other codes in other systems and they said it had a C1109 code (battery voltage out-of-range) in the ABS module, and the battery had been replaced a few weeks ago. I told them to make sure that the charging system was working properly and get back to me with what they had found.

The next day the Maxima was dropped off after the shop said they had checked out the charging system, so it must be the transmission. The shop uses the same Midtronics analyzer that we do and it has been pretty reliable. After verifying the issue, I started my standard evaluation. I follow the same procedure on every vehicle: check the transmission fluid, check the engine oil, use the pre-scan function on the Zeus workstation to scan all modules on the vehicle, and then check the battery and charging system. My test of the battery/charging system passed, lining up with what the shop had reported. I did pull the same C1109 code that was stored in the ABS module, but the P0868 had still not returned.

I then headed off for a road test. For most of the test drive everything was working well until I got about three blocks away from our shop. When accelerating from a stop the car just acted like it shut down. Throttle input was lost, and then it came back for a second, and then dropped out again. It had gotten so bad that I pulled off into a parking lot and walked back to the shop thinking the vehicle would not make it back on its own.

I checked out a few other vehicles at the shop and then went back to see if I could get the Maxima to make it back, which I did. I scanned for codes again and the C1109 was in the ABS module again. I wondered why the ABS module was the only module to set a code, but the issue seems to be affecting the transmission? I figured that I would just go to the source and monitor the battery voltage at the battery thinking that if anything, I would lose charging voltage due to a bad alternator. What actually happened was entirely different, however.

The voltage shot up past 19 volts on the meter. If you look at the results (FIG 1), each time the voltage goes down to a proper level the RPMs on the engine go up, and when the voltage goes high we lose throttle and the RPMs come back down. That screenshot was the most consistent example I had saved, and it also seemed to happen more consistently when I was accelerating heavier at lower speeds. When I got back to the shop I started doing a visual inspection thinking that the engine torque (torsional movement) was somehow affecting this.


Figure 1

I spotted a two-wire plug on the alternator that did not quite look right. (FIG 2) When I went to unplug it to check terminal fit and to make sure it was not corroded, it simply pulled right off. It was not plugged in all the way! We use a product called Deoxit for electrical connections. It has done a really good job for us for cleaning corrosion, and it also improves conductivity, so I sprayed some of that on the connector and plugged it back in making sure that the locking tab was engaged and went off for another road test.


Figure 2

Everything now was working well with voltage stable and no more cutting out and losing the throttle. I also did an extended road test to see if the transmission code would return and it did not. We called the shop and told them what had happened and what we did, and they were really surprised at the results and wanted to pay the diagnostic charges so their customer did not have any expenses. They called the customer to let them pick up the car directly from us and they were extremely happy that they did not have the expense of replacing the transmission.

It has been a few months since this happened so I had the service advisor call the customer just to see if everything was still working well, and I’m happy to report that no transmission issues have arisen everything was still working as intended.
It’s important to think about all of the conditions that are occurring when an issue exposes itself. In my case, it was the movement of the engine that was making the concern intermittent and elusive. That was the clue that helped crack the case.

Broken Snap Ring Creates OSS Codes

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.




Here in the Midwest the dog days of summer are here, creating a hot, humid environment and the intermittent issues that seem to come with it. You know…the types of concerns in which you have to drive the vehicle for an extended road test, and by the time you see what the issue is and get back to the shop, the heat from the engine compartment or under the vehicle is almost unbearable and you can’t touch anything without heat resistant gloves on. Good times.

That is where this story starts. A 2011 Chevrolet HD2500 6.6L equipped with a LCT1000 transmission came into the shop with a customer concern of no reverse and the indicator under the “R” is flashing. No power when pulling from a stop, and it won’t shift into higher gears on highway. Over the past few months we had seen a rash of bad Allison TCM’s with various different complaints, so I wondered if this might have been the case with this vehicle.

I started the evaluation by scanning all modules for DTCs and I found a P0721 “output speed sensor performance” code, and a P0722 “OSS low voltage” code, so this one appeared pretty straight forward, at first glance. Off I go for a road test intending to focus my attention to the OSS PID, so I set up the scan tool in graphing mode and saw that after about ten minutes while slowing down, the OSS signal drops out. (Figure 1)


Figure 1

When I went to take off from the stop light the truck was in failsafe, so I pulled over and checked for codes and found the P0722 had returned. I went back to the shop to finish the evaluation and take a closer look at the OSS. I performed a battery and charging system test which passed, so I let the vehicle sit for a couple hours while I checked out a few more vehicles. When I got back to it and went to unplug the OSS connector, the locking tab broke right off. The connection looked ok, as I saw no corrosion and the pin drag was good. I then unscrewed the sensor to make sure it was not mechanically damaged in some way, which it was not. I put my finger into the hole to make sure the reluctor ring was not damaged or loose, but I did not really expect to discover anything wrong there since it was a low voltage code I was chasing. It appeared to be ok.

At this point I could have taken a different path, but I don’t think the outcome would have been any different. We have all seen our fair share of these plastic screw in sensors have issues in the past and I had looked over the wire harness routing as per the PI#0339C and did not see anything wrong with it, and we had a sensor in stock so I ordered the repair pigtail from GM and proceeded to replace the OSS and pigtail feeling fairly confident it would correct the issue. After another extended road test, you guessed it…the speed sensor signal dropped out again very similar to the first screenshot, but this time it had set a P0721 code. In retrospect I knew I should have sold diagnostic time to the customer and put a scope on the sensor, so now the diagnosis time is on me.

I connected the scope to the OSS right at the connector and headed out again, not really expecting to see a problem here since it was a new sensor and pigtail. The reluctor was not damaged, so I was really thinking it would end up being a wiring issue or a bad TCM.

After another long road test the OSS signal on the scope and the data PID both dropped out at the same time. What? Did I have a bad “new” sensor? Remember when I said I don’t think the outcome would have been any different? If I would have done this from the start I really think I would have still put a sensor in it.

I brought the truck back into a bay and removed the sensor while it was blazing hot. I think it was about 96°F that day, and I bravely stuck my finger into the t-case to check the reluctor again and I finally discovered the real issue: while the ring would not spin on the shaft (it is splined onto the shaft), it did slide forward and backward. Figure 2 shows when I pushed it forward, and Figure 3 is when it was pushed back toward the driveshaft.


Figure 2



Figure 3

When it was forward the teeth were barely in the middle of the hole, and the sensor pickup is only about a 1/8th wide. This appeared to be the issue. I put it back together and went out again to try to verify it, and was able to. Look at each one of the dropouts when I quickly applied the brakes. (Figure 4) This confirmed that the issue was inside of the transfer case. After the transfer case was removed and I pulled the rear case half I could see what had happened: the snap ring on the backside of the rear bearing was broken into pieces. (Figure 5) This allowed the output shaft to slide forward just enough so that when the reluctor was at the forward end of its travel, it was enough to move it out of the sensors range and lose the signal. We ordered a couple snap rings and a rear bearing, made sure all the pieces of the broken snap ring were accounted for, and put it all back together. Now working as designed, no codes returned and we were able to deliver the truck back to the customer.


Figure 4



Figure 5

Expect the unexpected.

Mopar Fix for RAM ProMaster Transmission Bracket Breakage

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 our retail locations had a 2015 Ram Promaster show up on the back of a tow truck a few weeks ago, and this truck is a service vehicle for a local grocery store. The driver said he was traveling at about 40MPH when he felt like he ran over a boulder in the road, heard loud noises, and the truck stopped moving. This is the first time that I have seen this happen; the transmission was hanging down so far it was almost on the ground. What the heck happened?

We carefully pushed it into the shop so we could try to raise the transmission up and secure it so no more damage could occur, it almost appeared that the heater hoses were the only thing holding it up as they were stretched tight. After we were able to get the transmission lifted up and secured with a chain we were then able to see what happened, the left transmission (Chrysler calls it an engine mount) mount bracket and the transmission case were broken. There was a lot of damage done: case broken, mount bracket broken, both axles were damaged, shift cable broken, and air intake tube was torn. What we did not know yet is what caused this to happen. These photos were taken before we removed the transmission.

Figure 1


Figure 2


If this vehicle was traveling down the highway I’m sure it could have been much worse. There were wire looms that were at the verge of possible damage if it had dropped any further. We needed to find out why this happened and take the appropriate steps to make sure that it did not happen again. In a situation like this, if the root cause isn’t discovered there is a high probability of a customer comeback and another damaged transmission case.

We first looked for TSBs and came up empty, so I then contacted our technical director that is in charge of this unit model at our remanufacturing facility and asked if we were seeing cores come in that were broken like this. Sure enough we were, and he also informed me that the case for this particular application was just recently made available for sale from FCA. It was pretty clear that this was more of an issue than what I was initially aware of.

The next step I took was to call our local FCA dealer to check parts availability as I just wanted to make sure that everything was available to fix this vehicle before I turned this over for the service advisor to sell the job. This is where having a good parts professional to go to is always a good thing! After I gave him the VIN number and the parts that I needed, he said, “Hold on there are some notes on this one.” He then provided me with the paragraph below:

ALSO: This applies all Promaster (VF) 3.6L/62TE equipped vehicles. If the transmission bracket to the transmission case fasteners is removed during servicing, the fasteners (Part Number 06511385AA) are one time usage, and must be replaced. Vehicles built prior to 10/23/2015 require Service Kit PN 68461214AA; includes Transmission Isolator PN 68264483AA, and Adaptation Bracket 68264479AA, Fastener Service Kit PN 68329056AA. Vehicles built after on or after 10/23/2015 will require only the Fastener Service Kit PN 68329056AA (Please note that part #’s are subject to change, please check with your parts supplier) The production date on the vehicle we were working on was before 10/23/2015, so according to the notice we knew that we needed the complete service package.

With this newfound knowledge in mind, I was fairly confident that we could install a remanufactured transmission along with the updated parts and not have this issue after we completed the repairs. What I didn’t know at this point is exactly what was changed with the new bracket, isolator, and bolts.

Figure 3


This is the updated bracket compared to the OE piece, and it’s hard to tell from the picture but the new one had a lot more mass to it.

Figure 4


This is one of the new side bolts which are longer, have threadlocker compound on it, and even have some type of lubricant between the washer and head of bolt which I presume is for a more accurate torque reading. You will also need to remove the left headlight to properly torque the top mount bolt.

Please refer to service information for the complete procedure to install the mount, but I will cover the highlights here:

Note: Mopar lock & seal adhesive must be used on mount fasteners to prevent vibration loosening.

  1. Hand start all five transmission bracket bolts, starting with the lower four and then the upper bolt.
  2. Using four NEW bolts, beginning with the two outer, tighten all four side bolts to 77 ft-lbs.
  3. Tighten upper transmission bracket bolt to 46 ft-lbs.

I believe that if you were to tighten the top bolt before the side bolts, this would create undue stress on the case and bracket.

What I believe causes this issue is the mount bracket bolts coming loose; it is really hard to come to a 100% conclusion when they come in all broken apart like this but I can see evidence of movement of the bracket. In these photos you can see some wear on the boss that mates with the case, and there are thread grooves cut into the aluminum from the bolts which I would only think would be possible with movement of the bracket.

Figure 5


Figure 6

Programming Steps for 8L45/8L90 Units, Post Replacement

By Daniel Skinner, Diagnostician

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






Quite a lot has been been written and many technical classes have been put on regarding the General Motors 8L45/8L90 family of transmissions. We are now seeing opportunities to put that information to use. The vehicles equipped with these transmissions are beginning to trickle into our shops as they are beginning to fall out of factory warranty. Many GM vehicles utilize these transmissions from 2015 to present.

Our first vehicle to come in with 8L90 problems was a 2016 GMC Sierra 4×4. The truck had 103,000 miles on the odometer. The customer’s complaint was that the vehicle had a “shake” feeling below 70 miles per hour. He also that there was a “rumble” feel occasionally.

When evaluating the vehicle I noted that there was a P0711 (transmission fluid temperature sensor “A” circuit range/performance) code present. The transmission fluid was dark red with a slight burnt smell. During the road test I was able to reproduce the customer’s complaint. I experienced a repetitive, systematic vibration and droning sound throughout the vehicle at highway speeds. I was able to capture the issue using the scan tool.


Figure 1

This photo illustrates (Figure 1) TCC slippage and the TCM attempting to compensate/correct for it. The rhythmic shudder I experienced coincides with TCC slip speed captured with the scan tool. The transmission fluid temperature shown on the scan tool also explains the P0711 code. A sudden change in fluid temperature (50?F or more within 8 seconds) will cause P0711 to set. Obviously the transmission fluid temperature reading on the scan tool was unstable, so an electrical system analysis was performed to ensure battery and alternator integrity. Excessive AC ripple can play havoc on any electronically controlled transmission. A pan inspection was performed; evidence found in the pan along with the fluid condition had eliminated the possibility of trying to flush out the fluid with the Mobil 1 LV product, per a GM TSB.

At this point the customer agreed to replace the unit per our recommendation. After the unit was installed, solenoid valve characterization reprogramming had to be done. This is required when replacing 8L45/8L90 transmissions, and accomplished through General Motors’ TIS2Web Service Programming System (SPS). When performing solenoid valve characterization reprogramming, it is crucial to have a good clean power source connected to the vehicle’s battery and have all vehicle accessories turned off, as with any other programming procedure. Solenoid valve characterization reprogramming is fairly straightforward. After logging into the SPS website and purchasing a subscription for programming the vehicle you are working on (programming subscriptions are VIN specific), SPS will verify the vehicle/VIN you are working on. After SPS completes the verification, you will be directed to the screen shown in figure 2:


Figure 2

Highlight “K71/Transmission Control Module” in the “Select Controller” area. Then select “MCVM (Mechanical Characterization and Virtual Matching) Operations” in the “Select Function” area. Verify that the RPO code given coincides with the vehicle you are programming. Finally, be sure you select “Solenoid Data Characterization” in the “Select Programming Type” area at the bottom of the screen, and click “next”. The next screen will be the “MCVM (Mechanical Characterization and Virtual Matching) Operation Selection” screen (figure 3). Here you will be prompted to select what operation to be performed. In this case I chose “Replace Transmission”, as the unit had been replaced. Clicking “Next” will move you to the next screen (figure 4). Here you will enter the TUN (Transmission Unique Number).


Figure 3


Figure 4

This number can be found on a sticker on the right side of the transmission as seen in the “Transmission Identification Information” section of the screen. After entering the TUN and clicking “Next”, SPS will then begin the programming operation and prompt you when the process is completed. SPS seems to be user friendly regarding this process. I had no issues getting through it for the first time. At this point it is also recommended that the ECM (Engine Control Module) is updated to the latest calibration. The ECM on this particular truck happened to be up-to-date.

The next step in the process is to perform a “Fast Learn”. This clears all adaptive values in the TCM. Using your scan tool, follow the on-screen instructions precisely. Keep in mind that if at any time in the process, there is an interruption; you could experience a false neutral condition with the transmission. If this happens, you will have to disconnect and reconnect the TCM to correct the issue.

On the initial road test after installation, I experienced very minimal flaring during shifts. This flaring cleared up within a few miles of stop-and-go driving. This may vary from vehicle to vehicle. When rechecking the fluid lev-el, the transmission fluid level must be brought up to 194?F to ensure that the thermal bypass valve is open, if so equipped. Allow the fluid temperature to cool back down to 95-113?F. With the engine running, remove the transmission oil level plug from the transmission pan. At the correct level, fluid should drip from the check plug hole.

On the final road test, I monitored “TCC Slip Speed” and TFT (Transmission Fluid Temperature) with the scan tool. As you can see in (figure 5) the TCC slip speed is smooth and now normal. The TFT was stable as well. A post scan also confirmed that no codes reset.


Figure 5

Other than routine maintenance, this was the first major 8L90 issue we have dealt with. In the near future, I foresee many more 8L45/8L90 transmissions showing up. The torque converter issue we experienced on this vehicle is a problem that many dealerships have already encountered. Don’t be surprised to see these vehicles begin to show up at your shop, if they haven’t already.

Careful Visual Inspection Saves Time

By Travis Kraus, Diagnostician

author35Travis has been in the transmission business since 2003. He is from Topeka, KS and got his start at his dad’s shop sweeping floors. He came to Certified Transmission after 10 years as a transmission tech at a Ford dealer, and he has the A2 and A3 ASE Certifications and is working on more.




A customer showed up at our shop with a 2008 Chevrolet Impala SS that was equipped with the 5.3 LS engine and a 4T65E transmission. The customer had a complaint of an erratic speedometer while driving. I began by collecting all the vehicle information for a check out sheet, such as VIN, mileage, engine, and transmission type. After filling out the vehicle information section I set about to begin my diagnosis. First I checked codes and found the vehicle had no transmission or engine codes, but it did have a RF wheel speed sensor code which did not seem likely to cause the problem, but I kept this in mind anyway. I was suspecting a possible output speed sensor issue or maybe even an instrument cluster issue.

I set up my scanner to monitor certain transmission PIDs such as TCC duty cycle, TCC slip, gear command, RPM, and the output speed sensor (among others) and set out for my road test. At first the vehicle did not act up and I was starting to wonder if it even had a problem. After a couple of miles, sure enough the speedometer jumped back and forth a few times spiking as high as 60-70 mph just shortly after beginning to move; no way could this be correct. Every time this happened was when I took off from a stop, and this was a pretty good clue for me.

This told me I likely had a short somewhere and when the engine torqued it would cause the short and the malfunction. With this information in mind I returned to the shop and attempted to duplicate the issue by power-braking the vehicle quickly while in gear. Sure enough, I was successful in replicating the issue in the shop. You can see on the attached screen shot of the scanner when the problem occurred. (figure 1)


Figure 1

The vehicle speed PID goes from zero to 23 MPH instantly and the output speed sensor goes from 0 to 1010 RPM at the same time. I wanted to rule out possible interference from the alternator so I ran an electrical system check and ripple test which is standard operating procedure here, and no problems were found with the charging system. After this I decided to raise the vehicle and start looking for other possible causes. In the past I have seen internal transmission failures that drop large amounts of metal debris. This debris will stick to an output speed sensor and cause erratic readings of the output speed sensor.

I unbolted the speed sensor and pulled it out of the case and it was clean with no signs of concern, so I reinstalled it and started looking elsewhere. I always like to do a very good visual inspection before I break out the DVOM and do electrical checks. Many times I have found a concern with just the solid visual inspection. I started to follow the wire harness from the sensor back to the PCM. I noticed the plastic conduit surrounding the harness near a metal bracket on the transmission that secured the harness in place had deteriorated and fallen off. (figure 2)


Figure 2

I knew I was onto something with that discovery, and upon closer inspection I discovered a couple of wires had been chafed through the insulation and bare wires were exposed and grounding on the metal bracket. (figure 3)


Figure 3

Next I set off to identify these wires hoping to find they were a part of the output speed sensor circuit. I pulled up a wiring diagram for the output speed sensor on this car and identified the circuits as being a purple wire and a yellow wire as a twisted pair. With this information I went back to the car and as you can see in the picture, I had a chafed purple wire in a twisted pair with a yellow wire. This was certainly my problem. With my diagnosis complete I turned in this information to the service advisor to sell the work. The customer was happy to hear it was likely a simple problem and gave us the authorization to repair the wires and recheck.

At the initial inspection we did a pan inspection and the pan was clean and just had some old-looking fluid inside. We serviced the transmission and set off to repair the wire. We repaired the chafed wire and wrapped it back up with electrical tape and put some new conduit around it to protect it and prevent this from happening again, then secured it back in the bracket. With the service and repair complete and everything buttoned up, I set back off on a post-repair test drive to see if the problem was fixed. Everything worked as designed and the speedometer never exhibited a glitch again. I was happy with this so we notified the customer that his car was ready to pick up. The customer was eager to get his car back and get on the road with it.

We waited a couple of days and gave the customer a follow-up call to see how things were going with the impala. The customer was very happy and reported the car was working great and has not acted up since. The moral of this story is to never under estimate a good visual inspection. I have found many problems without the need to go into in-depth testing simply by looking around and paying attention to the small details such as plastic conduit that has fallen off a wire loom.