2002 Chrysler PT Cruiser in Limp Mode: P0605, P0551, P0700 Error Codes Explained
I own a 2002 Chrysler PT Cruiser with an automatic transmission, and it has recently entered limp mode. I took it to Advance Auto Parts for an OBD-II scan, but they couldn't identify the root cause of the issue. The diagnostic codes returned are: - P0605: PCM Read-Only Memory (ROM) Error - P0551: Power Steering Pressure Sensor Circuit Range/Performance - P0700: Transmission Control System Malfunction (repeated) The vehicle is now stuck in limp mode, and I'm concerned about potential transmission or electronic system failures. While the P0605 code suggests a possible PCM memory issue, it's important to note that this code can sometimes be triggered by software glitches or corrupted data rather than hardware failure. The P0551 code points to an issue with the power steering pressure sensor circuit—this sensor is located in the driver-side steering rack. It’s common for this sensor to fail due to wiring damage, loose connections, or physical disconnection during rack replacement. The repeated P0700 code indicates a malfunction in the transmission control system (TCS), which could stem from communication failures between the Transmission Control Module (TCM) and Powertrain Control Module (PCM). This may also be related to faulty TCM signals or relay issues. I recommend using a high-quality OBD-II scanner capable of communicating with both the PCM and TCM to verify signal integrity. A professional technician experienced in Chrysler transmission systems should inspect all relevant circuits, including power steering sensor wiring and TCM communication paths, before replacing any modules.
Yes, basic OBD-II scanners often can't diagnose these codes accurately—especially on older Chrysler models. You'll need a more advanced scan tool to confirm whether the TCM is communicating properly with the PCM and to test the actual circuit signals for the power steering sensor. The P0551 code is typically straightforward: the sensor is located in the driver-side steering rack, and it frequently gets disconnected during rack replacements or suffers from broken wiring or an open circuit. I strongly recommend consulting a technician experienced in Chrysler transmission and engine control systems before replacing any modules. Circuit checks should come first to rule out simple wiring or sensor issues.