Experiencing communication problems with your car’s diagnostic system can be incredibly frustrating, especially when it throws your vehicle into limp mode. Recently, I encountered just such a scenario with a 2006 PT Cruiser. This particular vehicle, a 2006 PT Cruiser, presented a classic case of OBD2 communication failure, preventing me from initially reading any diagnostic trouble codes. If you’re grappling with similar issues on your PT Cruiser, understanding the 2006 Pt Cruiser Obd2 Protocol and potential pitfalls can be the first step towards a solution.
Initially, the 2006 PT Cruiser in question wouldn’t start readily due to a weak battery from sitting idle for about ten days. After jump-starting and letting it run, it was clear there were underlying issues beyond just the battery. The check engine light (CEL) and ABS lights were illuminated, and the car was stuck in limp mode – a common symptom when the transmission defaults to second gear. My first hurdle was that my diagnostic scanner failed to communicate with the car’s computer system. This “CAN bus down/no communication” situation is a significant roadblock in modern vehicle diagnostics, as accessing the onboard computer is crucial for identifying problems.
However, things took an unexpected turn during a short test drive. To my surprise, the transmission started shifting gears! It cycled smoothly through all four gears, and the gear selector display (PRNDL) functioned correctly. For about 20 minutes, the PT Cruiser drove normally, exhibiting no driveability issues. This suggested that mechanically, the transmission might be sound, and the problem could be electrical or electronic. Upon returning to the garage, I quickly connected the scanner while the engine was still running. This time, the scanner immediately established communication and pulled a plethora of diagnostic trouble codes.
Here’s a breakdown of the fault codes retrieved from the 2006 PT Cruiser:
OBD II (7 codes stored)
- P1603 – PCM Internal dual port RAM communications failure
- P0700 – TCS (MIL Request) /Malfunction Indicator Light/
- U0101 – Lost Communications w/TCM
- P0562 – Battery Low
- P0700 – TCS (MIL Request) /Malfunction Indicator Light/
- U0101 – Lost Communications w/TCM
- P1603 – PCM Internal dual port RAM communications failure
SRS (Supplemental Restraint System)
- U1415 – Implausible data
- U1414 – Implausible ECU Network Configuration Data
ABS (Anti-lock Braking System)
- C100A – LF Speed Sensor Circuit
- U140E – Implausible Data
- C2202 – VIN Mismatch
- C2100 – Battery Disconnected
- C101F – RF Speed Sensor
- U0141 Lost communication w/Instrument Panel Module (FCM/TIPM) /front control module/total integrated power module/
- U0002 – Can C Bus Off Performance
Chrysler Specific
- P0700 – TCS (MIL Request) /Malfunction Indicator Light/
- U0101 – Lost Communications w/TCM
- P1684 – Battery Disconnected
- P0952 – Autostick Input Circuit Low
- P0613 – Internal Transmission Processor
- P0562 – Battery Low
It’s reasonable to initially discount the “Battery Low” (P0562) and “Battery Disconnected” (P1684, C2100) codes, at least for the moment. The battery’s weakness due to infrequent use is evident, and these codes could be a consequence of that. However, a weak battery can indeed trigger a cascade of seemingly unrelated error codes in modern vehicles, so it’s worth keeping in mind.
The “VIN Mismatch” (C2202) and “Implausible ECU Network Configuration Data” (U1414) codes initially suggested a potential ECU swap without proper programming. However, after clearing all the DTCs and restarting the engine, these codes did not reappear, at least not immediately. This could indicate they were historical or spurious codes.
After clearing all codes and taking the PT Cruiser for another drive, the limp mode returned immediately. This time, only a few codes resurfaced:
- C100A – LF Speed Sensor Circuit
- U0101 – Lost Communications w/TCM
- P1603 – PCM Internal dual port RAM communications failure
This narrowed down the immediate issues considerably. The fact that the transmission shifts normally when communication is established confirms the transmission itself is likely functional. The core problem seems to be electrical or electronic, possibly related to wiring harnesses or electronic control modules. The persistent C100A code points directly to the Left Front (LF) ABS wheel speed sensor circuit, suggesting a fault in the sensor or its wiring.
The recurring P1603 code, indicating a “PCM Internal dual port RAM communications failure,” is more concerning. Research suggests this can often be triggered by issues like:
- Faulty wiring, including poor grounds or power supply problems (blown fuses or relays).
- A failing Transmission Control Module (TCM) or Powertrain Control Module (PCM).
- TCM/PCM programming errors.
- Open or shorted circuits or connectors within the Controller Area Network (CAN) harness.
- Insufficient control module grounding.
Given the initial “CAN bus down” symptom, the U0101 “Lost Communication with TCM” code, and the P1603 code, the communication network and module power/grounding are prime suspects. It’s still unclear if the PCM in this 2006 PT Cruiser has been correctly programmed for the vehicle, especially considering the initial VIN mismatch code.
At this stage, further diagnostic steps are crucial. Checking the LF ABS sensor and its wiring, meticulously inspecting the CAN bus harness for any damage or corrosion, and verifying power and ground circuits to the PCM and TCM are logical next steps. Understanding the 2006 PT Cruiser OBD2 protocol is essential for interpreting these codes correctly and guiding further troubleshooting. Expert advice on diagnosing these complex electrical and electronic issues would be invaluable to efficiently resolve the limp mode and communication problems on this 2006 PT Cruiser.
