Refer to Theft Deterrent System in Electrical Diagnosis.
Circuit Description
The PCM controls fuel injector and starter operation based on a vehicle theft deterrent password from the Body Control Module (BCM). When the ignition is first turned on, the BCM sends a programmed password to the PCM. The PCM acknowledges the password and responds to the BCM that normal fuel injector operation will continue. If the PCM detects an incorrect password (Theft Deterrent 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 password from the Theft Deterrent 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 Theft Deterrent system. This condition can occur if an incorrect key is being used when attempting to start the vehicle or if the Body Control Module has been replaced and the PCM's password learn function has not been enabled. If the BCM 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 service procedures.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Perform the password learn procedure. Refer to Theft Deterrent Systems. Can the password learn procedure be performed successfully? | -- | System OK | Go to Theft Deterrent System in Electrical Diagnosis |
