Immobilizer DTC B389A Diagnosis and Repair

Circuit/System Description

The immobilizer system uses a unique environment identifier, learned by various modules during configuration, to prevent module swapping between vehicles. The Body Control Module (BCM) stores this identifier. Modules such as the instrument cluster, electronic brake control module (EBCM), HVAC control module, inflatable restraint sensing and diagnostic module (SDM), engine control module (ECM), and steering column lock control module (if equipped) learn this identifier. During operation, these modules compare their identifier with the BCM's. If they match, the vehicle can start. If they do not match, starting is disabled.

Conditions for Running the DTC

Ignition is in the ACCESSORY or RUN position.

Conditions for Setting the DTC

An incorrect environment identifier is stored by 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 will be cleared when the BCM learns a correct environment identifier.

Diagnostic Aids

If BCM programming is not completed after BCM replacement, the environment identifier may not be learned. If DTC B389A sets immediately after BCM replacement and programming, repeat the programming procedure.

Reference Information

• Schematic Reference: Refer to Immobilizer Schematics in Antitheft and Alarm Systems > Electrical.
• Connector End View Reference: Refer to Component Connector End Views in Vehicle > Connector Views > Connector End Views By Name.
• Description and Operation: Refer to Immobilizer Description and Operation in Antitheft and Alarm Systems > Components > Immobilizer.
• Electrical Information Reference:
  • Circuit Testing: Vehicle > Component Tests and General Diagnostics > Circuit Testing
  • Connector Repairs: Vehicle > Component Tests and General Diagnostics > Connector Repairs
  • Testing for Intermittent Conditions and Poor Connections: Vehicle > Component Tests and General Diagnostics > Testing for Intermittent Conditions and Poor Connections
  • Wiring Repairs: Vehicle > Component Tests and General Diagnostics > Wiring Repairs
• Scan Tool Reference: Refer to Control Module References in Vehicle > Programming and Relearning for scan tool information.

Circuit/System Verification

1. Verify DTC B389A did not set immediately following the replacement and programming of a BCM.
   • If the DTC set immediately after the replacement and programming of a BCM: The immobilizer learn procedure was not properly completed. Perform the BCM immobilizer learn using the Body Control Module IMMO Function with Existing Transponder or Remote Key in SPS. Refer to Immobilizer System Component Programming (without BTM) or Immobilizer System Component Programming (with BTM) in Antitheft and Alarm Systems > Programming and Relearning.
2. If the DTC did not set immediately after the replacement and programming of a BCM: Verify DTC B3902 is not set in any of the following control modules:
   • ECM
   • SDM
   • EBCM
   • HVAC control module
   • Instrument cluster
   • Steering column lock control module, if equipped
   • If DTC B3902 is set in any of the modules: Refer to DTC B3902 in ALL Diagnostic Trouble Codes (DTC) > B Code Charts > Immobilizer.
   • If DTC B3902 is not set in any of the modules: Perform the BCM immobilizer learn using Body Control Module IMMO Function with Existing Transponder or Remote Key in SPS. Refer to Immobilizer System Component Programming (without BTM) or Immobilizer System Component Programming (with BTM) in Antitheft and Alarm Systems > Programming and Relearning.
3. Verify DTC B389A does not set after programming.
   • If the DTC sets after programming: Replace the K9 body control module.
   • If the DTC does not set after programming: All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair. Refer to ALL Diagnostic Trouble Codes (DTC) > Verification Tests > Diagnostic Repair Verification.

For BCM replacement, programming, and setup, refer to Control Module References in Vehicle > Programming and Relearning.