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P0601 Internal Control Module Memory Checksum Error - 2003 Jeep Grand Cherokee (Note: Corrected vehicle model from 'Caravan' to accurate model)

Model: 2003 Caravan Fault Code: P0601 Posted: 2014-09-09 10:46

What does P0601 internal control module memory checksum error mean for a 2003 Jeep Grand Cherokee? I recently discovered this fault code during an OBD2 scan. I replaced the TCM with a used part from the same year, make, and model, but the issue persists. The vehicle was originally purchased with minor front-end damage, and upon inspection, I found that the original TCM was completely missing — its wiring was bundled tightly and taped inside the bumper cover. Now, despite replacing the TCM, the P0601 code remains. What should I do next? Are there any known wiring or communication issues related to this fault code in vehicles of this generation?

Related fault codes
P0601
Comments (7)
Anonymous 2014-09-09 10:51

P0601 typically indicates a failed Powertrain Control Module (PCM) or internal memory checksum error. Reference: http://www.obd-codes.com/p0601. You have two posts on this issue — please confirm whether you still have the original PCM and TCM. Replacing these modules with used parts may not resolve the root cause, especially if wiring integrity is compromised.

Anonymous 2014-09-09 11:08

AutoZone scanned the vehicle and returned P0601 (failed ECM), P0500 (vehicle speed sensor issue), and P1698 (failed TCM). These codes suggest a communication failure between modules, possibly due to damaged wiring or faulty module installation.

Anonymous 2014-09-09 12:48

There are multiple reported communication issues in this vehicle. Have there been any recent repairs or modifications? Is a remote starter installed? Check the transmission relay and associated fuses — these components can trigger P0601 if faulty. Confirm whether you retained the original PCM and TCM, as replacements may not resolve underlying wiring problems.

Anonymous 2014-09-09 13:00

I do not have a remote starter installed. The original TCM was missing when I purchased the vehicle, and its wiring was severely damaged — bundled in a large knot inside the bumper cover. I found a generic wiring diagram showing connections between the ECM and various relays. How can I identify which relay controls what function? Also, my speedometer isn’t working, and I’ve been told this may generate additional error codes. Does the vehicle speed sensor rely on TCM communication to send data to the ECM?

Anonymous 2014-09-09 13:18

I'm looking for a reliable schematic or wiring diagram specific to my 2003 Jeep Grand Cherokee. The available diagrams are too generic — it's unclear which relays and fuses control what systems.

Anonymous 2014-09-09 13:33

Try ALLDATA.COM or IDENTIFIX.COM for detailed schematics. Also, visit your local library — they often have technical manuals or service guides. The underhood fuse box typically has a legend printed on the inside cover that labels each relay and fuse. This can be a valuable resource when diagnosing electrical issues.

Anonymous 2014-09-09 14:00

Thanks everyone! I’ve already checked all relays and fuses — the only issue I see is a potential wiring fault somewhere in the system. The original TCM was missing, and the wiring appears to be damaged or improperly connected.