DTC Descriptor
DTC P1631: Theft Deterrent Fuel Enable Signal Not CorrectDiagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit/System Description
The theft deterrent module (TDM) sends the pre-release password to the engine control module (ECM) via the serial data circuit. The ECM then sends a challange to the TDM. 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 ACCESSORY or RUN position.
Conditions for Setting the DTC
The ECM receives an incorrect pre-release password from the TDM.
Action Taken When the DTC Sets
| • | The security indicator will illuminate. |
| • | Vehicle starting will be disabled or delayed. |
Conditions for Clearing the DTC
| • | A current DTC P1631 will be when a correct pre-release 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
Theft Deterrent System Schematics
Connector End View Reference
Theft Deterrent System Connector End Views
Description and Operation
Vehicle Theft Deterrent (VTD) 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 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.
Control Module References for ECM replacement, setup and programming.
