Which method is effective for clearing PCM codes on older trucks?

Disconnecting the power source for a brief period is an effective method for clearing PCM (Powertrain Control Module) codes, especially in older trucks. This process typically involves disconnecting the vehicle's battery cables, which cuts off power to the PCM and can reset the system. When power is restored, the PCM reinitializes, which often clears temporary fault codes that were stored due to historical issues. This method can be particularly useful for some older vehicles where diagnostic tools may not be readily available or where the PCM does not have the advanced features of newer models.

In older trucks, the PCM may not always support manual reset buttons or may not be easily reprogrammable without specialized equipment, making the power disconnection a more straightforward and accessible method for many mechanics and owners. While replacing the PCM may address persistent issues, it is a more drastic and costly step that should typically be considered after other diagnostic methods have been attempted.