P1631

Diagnostic Chart:

Refer to Power, Ground, MIL, DLC, in Data Link Communications, Data Link Connector and Key III in Theft Deterrent. Antitheft and Alarm Systems

CIRCUIT DESCRIPTION
The Vehicle Theft Deterrent (VTD) module produces the theft deterrent fuel enable signal when ignition is ON and the proper key resistor pellet is detected. The Powertrain Control Module (PCM) monitors the fuel enable signal during crank. If the proper signal is present on the Class II Serial Data Circuit, the PCM enables the fuel delivery in order to allow the engine to start. If the PCM detects an incorrect password (theft deterrent system failure or attempted vehicle theft, DTC 1631 is set. The engine may not start or crank as long as the condition is present. Refer to Vehicle Theft Deterrent (VTD) Description and Vehicle Theft Deterrent (VTD) Operation. Antitheft and Alarm Systems

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
- The PCM is detecting an incorrect password from the VTD system.
- The conditions is 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 theft deterrent system. This condition can occur if an incorrect key is being used when attempting to start the vehicle or if the Theft Deterrent Module has been replaced and the PCMs password learn function has not been enabled.