2002 PCM mystery - Multiple failures - interesting case
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2002 PCM mystery - Multiple failures - interesting case
2002 Ram 1500 with 4.7L, 166k miles. Truck runs great.
One day, the running (parking) lights stopped working.
Traced problem to an "open" in the PDC (Power Distribution Center/Fuse Block). In this year truck, the PDC is plugs and connections only, no electronics). Unfortunately, during the troubleshooting process, I got the following failures (the failures suddenly appeared during troubleshooting):
Disconnected battery (hard reset), drove vehicle. Code does not come back. Still have same 5 errors.
Replaced the FCM Front Control Module with the exact part number and revision - Still have same 5 errors.. I put the original FCM back in. Tested all relays and fuses. No change.
Note: The above failures are present with both the old and the new PDC. The only difference with the new PDC, is the running lights now work.
From what I gather by poking through the book is:
One day, the running (parking) lights stopped working.
Traced problem to an "open" in the PDC (Power Distribution Center/Fuse Block). In this year truck, the PDC is plugs and connections only, no electronics). Unfortunately, during the troubleshooting process, I got the following failures (the failures suddenly appeared during troubleshooting):
- ABS waring Light
- Speedometer does not work
- Brake warning light
- Airbag waring light
- A/C clutch does not engage
Disconnected battery (hard reset), drove vehicle. Code does not come back. Still have same 5 errors.
Replaced the FCM Front Control Module with the exact part number and revision - Still have same 5 errors.. I put the original FCM back in. Tested all relays and fuses. No change.
Note: The above failures are present with both the old and the new PDC. The only difference with the new PDC, is the running lights now work.
From what I gather by poking through the book is:
- If the PCM isn't reading the VSS, the speedometer, ABS, and A/C will not function.
- If the ABS module isn’t communicating with the PCM, you will get ABS and brake warning lights.
- If the PCM needs programming, the truck may not recognize critical signals (speed, A/C, airbag module)
- Did I short something out during my power-on troubleshooting? Did I cook the PCM?
- Could it be a bad wire / loss of VSS signal / coincidentally a bad VSS module
- Could it be just the PCM reprogramming needed? If so, how do I do it - dealer?
Suggestions will be greatly appreciated.
Thanks
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Joined: Apr 2010
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From: Clayton MI
PCM shouldn't be able to 'forget' it's programming... at least, not without exhibiting other signs of a roached computer.... Plugging in a scanner, to see what the various systems are whining about would be a good start though...
