DTC P1631
Diagnostic Instructions
DTC Descriptor
DTC P1631: Immobilizer Fuel Enable Signal Not
Correct
Circuit/System Description
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
Schematic Reference
Immobilizer Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Immobilizer Description and Operation
Electrical Information Reference
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 Immobilizer Relearn procedure. Refer to
Immobilizer 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.
|
