Auto Systems and Repair
PCM (Power Train Control Module)
The powertrain or engine control module is a powerful computer that manages the engine’s ignition, fuel injection, and emission systems. In some vehicles, it may also control the operation of the automatic transmission and the anti-lock brake system.
Symptoms of Wear or Failure
- Check Engine Light illuminates with codes that cannot be repaired
- Several unrelated trouble codes are set simultaneously
- Vehicle may not start or run
- Poor engine performance
- Engine stalls while driving
Related Repair Advice
- Many vehicles have upgradeable software in their PCMs, so be sure to check for any Technical Service Bulletins (TSBs) that pertain to possible problems
- When replacement is required, use a new factory PCM and install the latest software
- A PCM can be mistakenly replaced when there was actually a defective engine sensor that was overlooked in the initial diagnosis
- The terms PCM and ECM/U (engine control module/unit) are commonly used interchangeably. Technically, the ECM controls only engine-related functions, while the PCM controls engine and transmission operation.
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