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

This diagnostic procedure supports the following DTC:

DTC P1631 Theft Deterrent Start Enable Signal Not Correct

The ignition is ON.

DTC P1631 indicates that the vehicle theft deterrent password that the ECM has learned does not agree with the password received from the VTD system. This condition can occur if an incorrect key is used when attempting to start the vehicle, or if the BCM has been replaced and the ECM Password Learn function has not been enabled. If the BCM has been replaced, the password must be relearned.