For 1990-2009 cars

### Circuit Description

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

Substitution detection is based on 5 correct responses from the following module:

• | Instrument Panel Cluster (IPC)

• | Rear integration module (RIM)

• | Driver door module (DDM)

• | Front passenger door module (FPDM)

• | Left rear door module (LRDM)

• | Right rear door module (RRDM)

• | Driver position module (DPM)

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. The RCDLR will only check the modules status to see the 5 correct matches when a battery reconnect has been recognized within the theft deterrent module.

### DTC Descriptor

This diagnostic procedure supports the following DTCs:

DTC B0996 Engine Control Module VIN Checksum Error

The vehicle has DTCs including the DTC symptoms. Refer to DTC Symptom Description for more DTC information.

DTC Symptom | DTC Symptom Descriptor
--- | ---
00 | No Additional Information

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

• | The VIN check flag of the theft deterrent control module is TRUE.

• | The RCDLR has determined that the battery has been reconnected after disconnection.

### Action Taken When the DTC Sets

• | It may be impossible to start the vehicle.

• | The RCDLR sends the fuel disable message via the serial data circuit to the electrical system control module.

• | The remote control door lock receiver (RCDLR) will run the VIN Timer for a programmable length of time, typically 10 minutes.

• | The RCDLR will send a message to the IPC to flash the SECURITY indicator.

### Conditions for Clearing the MIL/DTC

• | The RCDLR clears the current DTC when the correct VIN information is present.

• | The DTC can be cleared with the scan tool.

### Diagnostic Aids

The VIN information is stored during the Setup New RCDLR Module procedure on a GM SPO replacement part. When the manufacturer enable counter (MEC) is equal to 0 the VIN information cannot be changed. DTC B0996 will set when the RCDLR does not receive the required 5 correct VIN responses from the modules which report to the theft deterrent module.

### Test Description

The following numbers are corresponding to the steps in the diagnostic table.

1. The RCDLR compares the stored VIN of 7 modules to that of the dash integration module (DIM). If two of the 7 modules are mismatched to the VIN stored in the DIM, DTC B0996 will set.

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Theft Deterrent System Schematics Connector End View Reference: Theft Deterrent System Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | With a scan tool, select Keyless Entry under Body and Accessories. Go to RCDLR in data display. View the substitution detection selection. Do any of the substitution detection flags read YES? | Go to Step 3 | Go to Step 5
3 | Perform the setup procedure for affected module or modules. Refer to Control Module References for setup and programming. Were you able to successfully perform the procedure? | Go to Step 6 | Go to Step 4
4 | Replace the affected module. Refer to Control Module References for replacement, setup, and programming. Is the replacement complete? | Go to Step 6 | --
5 | Replace the remote control door lock receiver (RCDLR). Refer to Control Module References for replacement, setup, and programming. Is the replacement complete? | Go to Step 6 | --
6 |

1. Clear the DTCs with the scan tool.
2. Attempt to start the vehicle.

Does the DTC set again?

Go to Step 2

System OK