PCM (Powertrain Control Module)
A PCM, which stands for a powertrain control module, is a vehicle’s computer that provides control over engine operation and virtually all other systems found in the vehicle. Unlike an engine control module and transmission control module, each of which is responsible for its own set of functions, a PCM combines both of them in a single unit.
Just about every aspect of your engine operation is monitored by your powertrain control module. It operates your fuel injection and ignition systems, emissions, transmission and many other engine related systems. In some cases, it is also responsible for the proper functioning of a traction control and anti-lock brake system.
While some drivers consider computerized engines to be very complicated, the others provide an array of benefits against a higher cost and complexity of such systems. Thus, a PCM allows your engine to run at its peak efficiency as well as prevents severe damage to the engine by alerting you of different issues before they ruin it.
Your powertrain control module operates different warning lights on your dashboard, including the check engine light, low oil warning lights and many others. For example, if the level of oil gets lower than the “min” mark, your PCM will illuminate the low oil warning light. In addition, your PCM comes with a built-in memory block where it stores all diagnostic trouble codes for ease of engine troubleshooting. In many cases, this allows a mechanic to find out the root of a problem in less than no time using a special scan tool.
Since your PCM is responsible for all vital functions in your vehicle, its failure will cause a variety of troubles. Here are the most common of them:
- Diagnostic trouble codes which do not refer to any existing issue
- Trouble codes stored to the PCM’s memory from unrelated engine systems
- Inability to start the engine or shift
- Reduced engine performance
- Stalling or rough idling
Powertrain control module maintenance
- If you have a PCM with upgradeable software, check for software updates from time to time to prevent possible problems.
- Use only an original PCM with the latest software as a replacement if the latter is required.
- Your PCM should be properly diagnosed before replacing. Some signs of a bad PCM can be caused by a faulty sensor or engine component.
- While PCM and ECU are often used interchangeably, they are different parts that are not interchangeable.
- Be sure to disconnect the battery before removing your PCM to prevent its failure.
- Before using jumper cables make sure to read the user’s instructions to prevent damage to the PCM and other electronic devices in your vehicle.