P1631

DTC P1631

DTC DESCRIPTOR

DTC P1631
Theft Deterrent Fuel Enable Signal Not Correct

DIAGNOSTIC FAULT INFORMATION
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

CIRCUIT/SYSTEM DESCRIPTION
The theft deterrent module (TDM) sends the fuel enable password to the engine control module (ECM) via the serial data circuit. The ECM then challenges this password. Both the ECM and TDM perform a calculation on this challenge. If the calculated response from the TDM equals the calculation performed by the ECM, the ECM will allow vehicle starting.

CONDITIONS FOR RUNNING THE DTC
Ignition is in the RUN position.

CONDITIONS FOR SETTING THE DTC
The ECM receives an incorrect fuel enable password from the TDM.

ACTION TAKEN WHEN THE DTC SETS
- The security indicator will illuminate.
- Vehicle starting will be disabled.

CONDITIONS FOR CLEARING THE DTC
- A current DTC P1631 will be when a correct fuel enable password is received.
- A history DTC will be cleared after 40 malfunction free ignition cycles or when a scan tool is used to clear DTCs.

CIRCUIT/SYSTEM VERIFICATION

IMPORTANT: Because of normal system communications between the TDM and ECM, any theft deterrent B-codes must be diagnosed prior to the diagnosis of P-codes.

Perform the Programming Theft Deterrent System Components procedure. Refer to Programming Theft Deterrent System Components. The ECM should successfully complete the password learn and the vehicle should start.
- If the ECM does not complete the learn or vehicle starting remains disabled, replace the ECM.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Control Module References for ECM replacement, setup and programming.