B0996

DTC B0996

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC B0996
- Vehicle Electronic Control Unit (ECU) VIN Check Error




Circuit/System Description

After a loss of battery power has been restored, the theft deterrent module (TDM) will perform a check on the stored vehicle identification number (VIN). If the VIN is CORRECT, the TDM will run the VIN Timer for a programmable length of time, typically 10 minutes. The TDM will send a message via the serial data circuit to the instrument panel cluster (IPC) to illuminate the SECURITY indicator. After the VIN Timer has timed out, the security indicator will turn OFF. If the VIN is INCORRECT, the TDM will send the fuel disable password to the engine control module (ECM), via the serial data circuit. The immobilizer system considers this to be a tamper and will not allow the vehicle to start. The TDM will send a message via the serial data circuit to the IPC to flash the SECURITY indicator.


Substitution detection is based on correct response from the following modules: instrument panel cluster (IPC), export body control module (XBCM), driver door module (DDM), passenger door module (PDM). The modules compare their VIN to that stored in the VIN master on every ignition ON cycle and report their status to the theft deterrent module.


Conditions for Running the DTC

Ignition ON


Conditions for Setting the DTC

* The VIN check flag of the TDM is true.
* The TDM has determined that the battery has been reconnected after a battery disconnect.



Action Taken When the DTC Sets

* The vehicle will not start.
* The TDM sends the fuel disable message via the serial data circuit to the ECM.
* The TDM will run the VIN Timer for a programmable length of time, typically 10 minutes.
* The TDM sends a message to the IPC to illuminate the SECURITY indicator.



Conditions for Clearing the DTC

The TDM clears the current DTC when the correct VIN information is present.


Reference Information
Schematic Reference

Immobilizer Schematics (Immobilizer Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Immobilizer Description and Operation (Immobilizer Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for Scan Tool Information


Circuit/System Verification

1. With a scan tool, verify the stored VIN in the following modules matches the actual vehicle VIN:

* IPC
* XBCM
* DDM
* PDM


• If any modules stored VIN does not match the actual VIN, perform the setup procedure for that module. If the stored VIN does not match after setup, replace the module.

2. If all modules VIN match, replace the TDM.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for XBCM, TDM, IPC, DDM, PDM replacement, setup, and programming