Service Information

Cruze

DTC P1631

Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this 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: Immobiliser Fuel Enable Signal Not Correct

The body control module (BCM) sends the security code to the engine control module (ECM) via the serial data circuit. The ECM then sends a challenge to the BCM. Both the ECM and BCM perform a calculation on this challenge. If the calculated response from the BCM 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 security code from the BCM.

Action Taken When the DTC Sets

•	The security indicator in the instrument cluster will illuminate.

•	Vehicle starting will be disabled.

Conditions for Clearing the DTC

•	A current DTC P1631 will be cleared when a correct security code 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

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Note: Because of normal system communications between the BCM and ECM, any immobilizer B-codes must be diagnosed prior to the diagnosis of P-codes.

Perform the Immobiliser Relearn procedure. Refer to Immobiliser System Component Programming .

⇒	If the ECM does not complete the learn or vehicle starting remains disabled, replace the K20 Engine Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Control Module References

•	For P-codes refer to Diagnostic Trouble Code (DTC) List - Vehicle .