P1631

Refer to Theft Deterrent System Schematics in Antitheft and Alarm Systems.

Diagnostic Chart:

CIRCUIT DESCRIPTION
The PCM controls fuel injector and starter operation based on 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.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The PCM is detecting an incorrect vehicle theft deterrent password from the VTD system.

The conditions are present for less than 1 second.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will not illuminate the malfunction indicator lamp (MIL).
^ The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
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 being used when attempting to start the vehicle or if the VTD module has been replaced and the PCMs password learn function has not been enabled. If the VTD module has been replaced, the password must be relearned. Refer to Theft Deterrent Systems for VTD system service procedures.