GMC Terrain 2013 OBD2 Codes P0700 and P0606: Transmission Limp Mode & ECU Repair Cost Concerns
My GMC Terrain 2013 is showing a check engine light. The OBD2 scanner displays two fault codes: P0700 (Transmission Control System Malfunction) and P0606 (Memory Error in Powertrain Control Module). The vehicle appears to be in limp mode, which limits performance to prevent transmission damage. I consulted two mechanics—one suggested replacing the powertrain control module sensor (P0606) based on the code, while another quoted $1,100 for a full diagnosis and potential repairs. I'm concerned about the high cost and want to know whether it's safer or more cost-effective to follow the first mechanic’s recommendation of replacing the sensor, or if I should wait for a comprehensive diagnostic from the GMC-certified technician. What is the most reliable approach for diagnosing and fixing these codes in a 2013 GMC Terrain?
Begin by checking the powertrain control module (PCM) for supply voltage issues. If faulty, perform an ECU reprogramming before considering replacement. This step can resolve P0606 and related transmission faults without full part replacement.