QuestionQUESTION: My Insterment cluster works sometimes $ then other times it doesnt work at all. Along with this my trany has been shifting down to low all by it self. The light on the dash under the PRND3L juat moved under the L and the trany started to down shift. The only way to get it out of low was to shut off the car and start it again.
ANSWER: Hi Mike,
The communication between the powertrain controller, transmission controller, body computer and cluster is probably impaired in some way. The transmission responds by going into limp-in mode. The best thing to do is try the ignition key to see if there might be something specific stored in the engine controller memory. Turn it "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light which remains "on" to see it begin to "flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to be sure you have an accurate set of counts. Then tell me the numbers you got in the order of appearance. The transmission controller also has a memory that is accessed with a code reader via a plug that is under the dash. That can be done at an independent trans shop or dealer who has an OBD-1 data link connector for Chrysler cars (less costly perhaps at an independent shop). Similarly let me know what you learn including the specific code number and be sure to distinguish between numbers from the engine or the trans memory. The numbers are 2-digits, but they overlap and thus can be confused unless you determine which memory is being read.
It may just be a problem with the wiring of the data communication bus, or it could be a problem with one of the components in the shared system. The limp-in is self-protective to minmize damage to the trans until this can be diagnosed and corrected. You might try tapping on the top of the cluster when it fails, as a loose solder joint at the plug socket/circuit board interface can cause this by itself. Let me know what you learn.
Roland
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QUESTION: Code 12 and Code 66:
Code 12 seems to mean - problem with battery connection - direct battery to control unit disconnected within last 50 ignition on cycles.
Code 66 seems to mean PCM not receiving CCD bus signal.
What do these things mean? Can you tell me how to fix?
Would replacing PCM fix problem? Or is problem possibly connected to VSS?
Thanks,
Mike
ANSWER: Hi Mike,
I would begin by checking the plug and harness from the transmission control module that goes to the powertrain controller. The tcm is on the right inner fender near the front of the engine compartment, the pcm is on the left inner fender. See if that helps.
If not, then I would unplug the battery for a few minutes which should erase the 66 code, but don't try to verify that, just reattach the battery.
Then disconnect the TCM and turn the ignition to the run position and then off. Then do the fault code check. If the 66 code is not back then it suggests replacing the TCM. If the 66 code is back, then reconnect the TCM and disconnect the PCM. Then turn the ignition to run position and then off. Then do a code check. If the 66 code is not back then it suggests replacing the PCM...
continue in the same mode trying each of the other possible items in the data bus: abs, traveller, instrument cluster, theft system, trip computer, air bag control, automatic temp control, ... until you find one that when disconnected doesn't cause the 66 to come back.
This approach normally is done using the diagnostic readout box, so I can't be sure that it will work exactly the same using the ignition key, but give it a try. If none of the item is implicated then I would check out the continutity of the plug between the transmission controller and the powertrain controller. Let me know if that is the case.
Roland
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QUESTION: The reason I thought it might be PCM is because my air conditioner vent operating system doesn't work any longer and only blows out of defrost vents. Is that system controlled by PCM or is that system controlled by body computer systems? And the morning, a new problem was the cluster would not come on and the car would only start and die. A few minutes later, everything was fine. Please let me know, I'm chasing my tail!
Thanks, Mike
AnswerThe hvac is controlled by the body computer and its own panel (mention whether ATC or conventional when you reply, though).
It still seems to be something with the CCD bus system as that is needed to run the cluster too. It is apparently intermittent. That is about all I can conclude at this point. So try the analytic approach and watch for any other codes.
Roland
