Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P1631: Theft Deterrent Fuel Enable Signal Not CorrectCircuit/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. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Immobilizer Description and Operation
Electrical Information Reference
Scan Tool Reference
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 Control Module References
| ⇒ | 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.
Control Module References for ECM replacement, setup and programming
