The powertrain control module (PCM) controls fuel injector and starter operation based upon a vehicle theft deterrent (VTD) password from the vehicle VTD module. When the ignition is first turned ON, the VTD module sends a programmed VTD password to the PCM. The PCM acknowledges the password and responds to the VTD module that normal fuel injector and starter operation will continue. If the PCM detects an incorrect password (VTD system failure or attempted vehicle theft), DTC 1631 will set. The engine will not start or crank as long as the condition is present.

The ignition is on.

The PCM detects an incorrect vehicle theft deterrent password from the VTD system.

The condition is present for less than 1 second.

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

DTC P1631 indicates that the vehicle theft deterrent password that the PCM has learned does not agree with the password being received from the VTD system. This condition can occur if an incorrect key is used when attempting to start the vehicle, or if the VTD module has been replaced and the PCM password learn function has not been enabled. If the VTD module has been replaced, the password must be relearned. Refer to Programming Theft Deterrent System Components in Theft Deterrent Systems .

Refer to Diagnostic System Check - Theft Deterrent in Theft Deterrent Systems for VTD system service procedures.