Tech Tip: GM PASSLOCK Relearn Procedure – UnderhoodService

Tech Tip: GM PASSLOCK Relearn Procedure

Vehicle will not start after the original ECM has been replaced. The original ECM has a security code (PASSLOCK) stored in its memory that matches the vehicle's instrument panel cluster or security module (if so equipped). The replacement ECM can only receive the PASSLOCK code after it is installed in the vehicle and a relearn performed on the ECM.

Models: All OBD-II (1996 and newer) GM vehicles equipped with the PASSLOCK anti-theft system. 
 
Problem: Vehicle will not start after the original ECM has been replaced.

Cause: The original ECM has a security code (PASSLOCK) stored in its memory that matches the vehicle’s instrument panel cluster or security module (if so equipped). The replacement ECM can only receive the PASSLOCK code after it is installed in the vehicle and a relearn performed on the ECM.

Solution: Because the procedure is vehicle specific, it will be necessary to reference the vehicle service manual for the correct procedure. 
 

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