When an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the transponder embedded in the key is energized by the exciter coils surrounding the ignition lock cylinder. The transponder transmits a signal to the body control module (BCM). The BCM then compares this value to a value stored in memory. If the value is correct, the BCM will send the prerelease password via the serial data circuit to the engine control module (ECM). If the learned key code does not match or a transponder value is not received, the BCM will send the start disable password to the ECM.

Ignition is in the Accessory or Run position.

The BCM is unable to measure the ignition key transponder value.

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

1. Inspect all available vehicle keys that they are correct vehicle keys.

⇒	If not a correct vehicle key, replace the key.

2. While viewing the scan tool BCM Transponder Key Communication, turn ON the ignition with each of the available vehicle keys. The parameter should read ID Received with all available keys.

⇒	If only one key results in the parameter reading Inactive, replace the appropriate key.

⇒

If all available keys result in the parameter reading Inactive, test the control circuit terminal 26 (X1) and 27 (X2) at the BCM for a short to voltage or an open/high resistance. If the circuit tests normal replace the K84 Remote Function Receiver Module and verify the parameter should read ID Received with all available key. If the parameter reading is Inactive replace the K9 Body Control Module (BCM)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.