Diagnostic Instructions
DTC Descriptor
DTC P1631: Theft Deterrent Fuel Enable Signal Not Correct
Circuit/System Description
The engine control module (ECM) controls the fuel injector operation based on a theft deterrent password from the 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 fuel injector 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.
Conditions for Running the DTC
Ignition is in the RUN position.
Conditions for Setting the DTC
| • | The ECM detects an incorrect password from the theft deterrent system. |
| • | The condition is present for less than 1 second. |
Action Taken When the DTC Sets
| • | The ECM will not illuminate the malfunction indicator lamp (MIL). |
| • | The ECM 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 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 ECM has learned does not agree with the password received from the theft deterrent 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.
Reference Information
Schematic Reference
Immobilizer Schematics
Connector End View Reference
Master Electrical Component List
Description and Operation
Immobilizer Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
Perform the password learn procedure. Refer to
Programming Theft Deterrent System Components
.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for BCM replacement, setup, and programming
