Sometimes everyone jumps into a repair without reading all of the appropriate service information; I’m guilty of this, too. Usually, when a vehicle “bites us on the backside,” after the smoke clears, the problem turns out to be something we could have avoided if we’d have started with the directions. That’s even true when programming issues are involved.
Keith Clark’s article, Pass-Thru Programming, in the October issue of GEARS is a great place to start if your shop isn’t programming yet. To quote Keith: “Of course, problems may arise when programming. Most problems are from not paying attention to the details.”
Keith was right on the money with that one. This month’s article will illustrate how thorough research can often solve technical issues.
A local shop called regarding an auction vehicle they’d purchased and prepared for resale. The vehicle was a 2007 Dodge Caliber and the transmission had to be replaced before it could be put on the lot.
The shop installed a used transmission and after the repair the transmission was in limp mode. Their call only yielded basic information: CVT replaced, limp mode, and “can you program it because the TCM is in the transmission?”
When a shop calls with an issue like this, our first step is to perform some research. This is the part of the job that many technicians skip, but it can be very valuable.
In this case I had only a little information to work with. They provided the basic vehicle information and requested the information to program the TCM.
Further conversation revealed that code P167A — Calibration Mismatch — was stored in memory, which would seem to suggest the used transmission had an internal module that didn’t match the vehicle. With all that in mind, it was time to do some digging:
Checking service information pertaining to transmission replacement would be important, as would checking TSBs (Technical Service Bulletins). Research on the Chrysler service information site revealed the TCM isn’t inside the transmission as the shop suggested, but there is a solid state component in the CVT.
In addition, transmission and TCM replacement procedures differ as they pertain to programming. If the TCM were internal, the TCM and transmission replacement procedures should be the same.
As soon as I arrived at the shop, I took the car on a test drive; it was in limp mode. A wiTech confirmed code P167A in memory. Because this code indicates a calibration mismatch, I checked other information to see if I could confirm the mismatch (figure 1)
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The VIN in the TCM matched the vehicle and all ECU information for the PCM and TCM seemed to be in order. So the TCM matched the vehicle and all of the software calibrations seemed to match. So how could we have a calibration mismatch? We decided to try reprogramming and see if it resolved the issue.
We reprogrammed the PCM/TCM and initialized the TCM. Then we went for a test drive. Within minutes the car was back in limp in mode. But this time we found code P0602 — Control Module Programming Error/Module Not Programmed.
At this point I could only assume we missed something, so we started back at the beginning: We knew we performed all appropriate steps during a transmission replacement as listed in the service information.
A second TSB search revealed a bulletin we’d missed earlier: Bulletin 18-019-06 showed up while searching code P0602; not P167A. It said the PCM and TCM need to be reflashed together to be the calibrated with the latest matching software. We’d already performed this procedure, so it shouldn’t have been an issue. But what did we have to lose reprogramming them again?
We repeated the whole procedure and the results were the same: Limp in mode occurred before the vehicle even made it off the lot. Well, back to the old drawing board.
During a bit of head scratching, we found some bold print near the end of the TSB (figure 2).
Could the simple steps at the end of the TSB be our whole problem? An inappropriate sequence of cycling the ignition? No, it couldn’t be… the scan tool never told us to cycle the key and wait. But it was.
We reprogrammed the PCM and TCM, this time including the appropriate key cycles and pauses to resolve the problem.
In this case, reading all the information thoroughly the first time around would have saved us some time and resolved the issue much earlier. We were also lucky the error didn’t damage the TCM or PCM, which could have easily been the result of an incorrect programming event on some vehicles.
There’s an old expression that goes, “when all else fails, read the directions.” On the other hand, if you’d like to avoid the problem entirely, read the directions first.
