How to Reset a GM PCM

The powertrain control module (PCM) in General Motors vehicles is the main computer responsible for controlling most of the vehicle's computerized components including the engine, transmission and drivetrain. When the PCM detects a problem with one or more of the vehicle's components or systems it stores a trouble code in its internal memory and illuminates a malfunction indicator light (MIL) on the dashboard. An automotive scan tool is required to clear the codes and reset the PCM.

Step 1 - Shift the vehicle's transmission into park or first gear. Shut down the engine and set the parking brake. Rotate the ignition back to the "On" position but don't start the engine.

Step 2 - Plug the scan tool's data cable into the vehicle's diagnostic data port, located underneath the dashboard on the driver's side.

Step 3 - Turn on the scan tool and allow it to boot up. Follow the on-screen instructions to enter in the vehicle's specific drivetrain information.

Step 4

Select "PCM" from the scan tool's main menu. Choose "codes," then select "clear all current and stored DTCs." DTC is an acronym from diagnostic trouble code.

Wait for the scan tool to confirm that the codes have been cleared. Disconnect the scan tool from the vehicle and start the engine. Verify that no MILs are illuminated in the gauge cluster. The PCM is now reset.

TIPS: Automotive scan tools are small computer units that communicate with the computers in passenger vehicles in order to diagnose problems. They are available from auto parts stores and automotive tool resellers.

THINGS YOU'LL NEED: Automotive scan tool

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