Experiencing trouble with your 2005 PT Cruiser? OBD2 codes can be a crucial starting point in diagnosing car problems. Recently, while working on a 2006 PT Cruiser that had been sitting idle, I encountered a series of diagnostic trouble codes that shed light on potential issues, and the process can be very relevant for 2005 models as well. Even though the vehicle hadn’t been started for about ten days and had a slightly weak battery, it presented a valuable case study for understanding OBD2 diagnostics in these cars. Initially, communication with the scanner was impossible, and the car was stuck in limp mode, limiting transmission to 2nd gear.
However, after charging the battery and allowing the car to warm up, an unexpected improvement occurred. The transmission began shifting correctly through all gears, and the PRNDL displayed the selected gear accurately. This positive change allowed for a successful connection with the OBD2 scanner while the car was running, revealing a collection of stored fault codes. These codes, while initially numerous, provided essential clues for diagnosing the underlying problems. Let’s delve into these codes and what they might indicate for your 2005 PT Cruiser.
Initial OBD2 Codes Retrieved
Upon connecting the scanner, a range of codes were present across different systems:
ODB 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 (2 codes stored)
- U1415 – Implausible data
- U1414 – Implausible ECU Network Configuration Data
ABS (7 codes stored)
- 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 (6 codes stored)
- 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 important to note that codes like P0562 (Battery Low) and P1684 (Battery Disconnected) could be related to the car sitting idle and the weak battery. Low voltage can indeed trigger various fault codes, and in this case, a battery load test might be advisable.
Initially, codes such as C2202 (VIN Mismatch) and U1414 (Implausible ECU Network Configuration Data) suggested a possible ECU swap without proper programming. However, after clearing all DTCs, these specific codes did not reappear immediately.
Persistent OBD2 Codes After Clearing
After clearing the initial set of codes and restarting the vehicle, the PT Cruiser reverted back to limp mode. A subsequent scan revealed a much shorter list of persistent codes:
- C100A – LF Speed Sensor Circuit
- U0101 – Lost Communications w/TCM
- P1603 – PCM Internal dual port RAM communications failure
These codes are more critical as they reappeared after clearing, indicating ongoing issues.
Decoding the Persistent Codes for a 2005 PT Cruiser
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C100A – LF Speed Sensor Circuit: This code points directly to a problem with the Left Front (LF) wheel speed sensor circuit. This could be the sensor itself, the wiring to the sensor, or the connections. A faulty speed sensor can affect ABS, traction control, and transmission shifting. For a 2005 PT Cruiser, checking the LF speed sensor, its wiring harness, and connector is a crucial step.
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U0101 – Lost Communications w/TCM (Transmission Control Module): This is a communication fault, indicating that the PCM (Powertrain Control Module) is losing communication with the TCM. This can lead to transmission problems, including limp mode. Potential causes can range from wiring issues in the CAN bus network, a faulty TCM, or even PCM problems.
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P1603 – PCM Internal dual port RAM communications failure: This code suggests an internal fault within the PCM related to its dual port RAM communication. While it could indicate a faulty PCM, online research suggests that wiring problems like poor grounds, power supply issues (fuses, relays), or a faulty TCM/PCM itself can also trigger this code.
Troubleshooting Steps for Your 2005 PT Cruiser
Based on these persistent codes, here’s a logical approach to troubleshooting your 2005 PT Cruiser:
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Address the C100A Code (LF Speed Sensor Circuit):
- Inspect the LF Speed Sensor: Check for physical damage, debris, or loose connections.
- Check Wiring and Connectors: Examine the wiring harness and connector for the LF speed sensor for any signs of damage, corrosion, or breaks.
- Test the Sensor: Use a multimeter to test the resistance and signal output of the speed sensor.
- Consider Replacement: If the sensor or wiring is faulty, replacement might be necessary.
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Investigate U0101 and P1603 (Communication Issues):
- Check Battery Voltage and Connections: Ensure the battery is fully charged and the terminals are clean and tight. Low voltage can cause communication problems.
- Inspect Fuses and Relays: Check the fuses and relays related to the PCM and TCM in the power distribution center.
- Examine CAN Bus Wiring: Look for any damage or corrosion in the CAN bus wiring harness.
- Check Ground Connections: Ensure all ground connections for the PCM and TCM are clean, tight, and free from corrosion.
- Evaluate TCM/PCM: Consider the possibility of a faulty TCM or PCM. This is often a last resort, but these modules can fail. Programming issues could also be a factor, especially if there’s a history of ECU replacement.
Conclusion
Diagnosing OBD2 codes in a 2005 PT Cruiser requires a systematic approach. Starting with the retrieved codes, particularly the persistent ones like C100A, U0101, and P1603, provides a clear direction for troubleshooting. Addressing potential issues with the wheel speed sensor circuit and investigating communication problems within the CAN bus network, along with ensuring proper power and ground to the PCM and TCM, are essential steps. While the initial VIN mismatch codes were concerning, their disappearance after clearing suggests they might have been related to the car’s idle state or low battery voltage. Focus on the recurring codes to effectively diagnose and resolve the drivability issues in your 2005 PT Cruiser. Remember to always consult a repair manual specific to your 2005 PT Cruiser for detailed procedures and specifications.
