P1631

Circuit Description
The PCM controls fuel injector operation based on a vehicle theft deterrent password from the PASS-Key(R) III module. When the ignition is first turned ON, the PASS-Key(R) III module sends a programmed password to the PCM. The PCM acknowledges the password and responds to the PASS-Key(R) III module that normal fuel injector operation will continue. If the PCM detects an incorrect password (PASS-Key(R) III system failure or attempted vehicle theft), DTC 1631 will set. The engine will not start as long as the condition is present.

Conditions for Setting the DTC

The PCM is detecting an incorrect vehicle theft deterrent password from the PASS-Key(R) III system.

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 Fail Records data only. This information will not be stored as Freeze Frame data.

^ The PCM will disable the fuel injectors.

Conditions for Clearing the MIL/DTC

^ A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

^ DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

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 PASS-Key(R) III system. This condition can occur if an incorrect key is being used when attempting to start the vehicle or if the PASS-Key(R) III module has been replaced and the PCMs password learn function has not been enabled. If the PASS-Key(R) III module has been replaced, the password must be relearned using approved Techline diagnostic equipment.

Refer to Theft Deterrent System in Electrical Diagnosis for further diagnosis.

Refer to On-Vehicle Service in Theft Deterrent Systems for PASS-Key(R) III system service procedures.