- Author: Jerry Huerter
- Subject: No TCC lockup
- Unit: Jatco JF011E CVT
- Vehicle Application: 2007 Dodge Caliber
- Essential Reading: Rebuilder, Diagnostician, R&R
When a vehicle comes into your shop for repair you need to determine whether you have access to service information, the equipment needed to make the repair and the experience to repair it. As you read this article you will see just how challenging a transmission replacement sometimes can be. In this particular situation the service information was misleading and special equipment was needed to make the repair. This was one job that turned into yet another learning experience for me.
A 2007 Dodge Caliber with a continuously variable transmission came into our shop. It previously had been at another shop that had replaced the transmission with a used unit. The customer said that after installation, the used transmission seemed to slip and the check engine light came on. When I scanned the TCM I found codes P0843, secondary oil-pressure-sensor circuit high; P0741, torque-converter-clutch circuit performance; and P167A, calibration mismatch. After clearing the codes I took the vehicle for a test drive. The transmission seemed to work OK, but the engine speed seemed a little higher than normal. The P167A code reset as soon as the ignition was turned on and the P0741 code reset during the short test drive. The P0843 code did not reset.
Service information said that this CVT uses the torque converter for launch only, then locks up the converter around 12 mph. The P0741 code sets when the TCM detects excessive TCC slip for 30 seconds, and it takes two failures to set the code. This explained why the engine speed was higher than normal, but the question was, what is the cause of the TCC not locking up? The P167A calibration-mismatch code will set when the information in the TCM does not match the information in the ROM chip inside the transmission. I decided the P176A should be diagnosed first. The service information said a relearn procedure needed to be performed on the TCM. I searched and found service bulletin #18-019-06, which says if the check engine light is on and DTC P0602, P167A and/or P161B is present both controllers (TCM and PCM) must be reprogrammed.
The TCM reflash was successful but the ECM reflash failed. The electronic throttle was now limited to around 6%, which is just above idle, and the vehicle was no longer drivable. I used a J2534-1 programmer, which is an early model. Since this was a CAN vehicle I suspected that the programmer I had used was the reason for the reflash failure. My son Ryan, who operates a reflash business, brought his J2534-2 programmer over. His programmer flashed both the TCM and PCM successfully.
When I started the vehicle the check engine light was not on and no P167A code set. I then took the vehicle for a second test drive. The electronic throttle now worked, the TCC locked up and the engine speed returned to normal. Everything seemed to be working properly. I shut the vehicle off and restarted it only to find that the check engine light was back on, the P167A code had set again and the electronic throttle went back to not working. So it was back to the drawing board!
After more research it looked as if the factory scan tool was the only way that the TCM could be relearned to accept a different ROM chip after a transmission replacement. I also found that some technicians are installing the original ROM chip in the replacement transmission. This chipset was programmed when the transmission was assembled and carries vital information on the variators and hydraulic system. The ROM should never be interchanged with that of any other CVT, since it is unique to the CVT it came with.
Now the vehicle needed to be taken to the dealer for relearning, but it couldn’t be driven because the electronic throttle control was restricting the throttle. Rather than having to tow the vehicle to the dealer I was able to locate a mobile troubleshooting company that came to my location. Using their factory scan tool they were able to relearn the TCM. After this procedure the operation of the CVT returned to normal.
Jerry Huerter, an ASE Master technician with L1 Advanced Engine Performance Diagnostics certification, is the head diagnostician at the Certified Transmission retail location in Overland Park, Kan.