GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The vehicle theft deterrent control module checks the theft deterrent exciter module key data signal circuit for a constant voltage condition.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2955 Security System Sensor Data Circuit

Conditions for Running the DTC

The theft deterrent control module must see the ignition switch input. The theft deterrent control module cannot have DTC B1327 set as a current DTC.

Conditions for Setting the DTC

The theft deterrent control module requires one second to monitor the ignition key. After the first second, the theft deterrent control module turns off the power to the theft deterrent exciter module. If the theft deterrent control module senses the key data signal to the theft deterrent exciter module is 12 volts for one second, the theft deterrent controller module sets this DTC.

Action Taken When the DTC Sets

Important: If the theft deterrent control module senses the sensor low reference circuit is 12 volts after the vehicle has started, the theft deterrent control module will enter fail enable state. The vehicle will not stall or stop running. If the theft deterrent control module is in a fail enable state when the ignition is turned to OFF, it will remain fail enable until the next time the vehicle is started. If the theft deterrent control module is fail enabled, the vehicle theft deterrent (VTD) system is NOT active and the vehicle will start.

    • Stores DTC B2955.
    • The vehicle will not start.
    • The theft deterrent control module sends a class 2 message to the instrument panel cluster (IPC) to illuminate the SECURITY indicator.

Conditions for Clearing the MIL/DTC

The theft deterrent control module clears the current status of the DTC when it does not sense a 12 volt condition on the theft deterrent exciter module key data signal circuit. The DTC will still be retrieved as current until the ignition switch is cycled. The DTC will become a history DTC at that time.

Diagnostic Aids

Refer to Testing for Intermittent Conditions and Poor Connections and Testing for Electrical Intermittents in Wiring Systems.

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 in Vehicle DTC Information

2

Is DTC B2955 set as a current code?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

Test the security system sensor low reference circuit for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 4

4

Inspect for poor connections at the harness connector of the theft deterrent exciter module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 6

5

Inspect for poor connections at the harness connector of the theft deterrent control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Replace the theft deterrent exciter module. Refer to Theft Deterrent Exciter Module Replacement .

Did you complete the replacement?

Go to Step 8

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7

Important: If a 10 Minute or 30 Minute Re-Learn Procedure is performed, all keys not learned at that time will be erased and will not be recognized. Perform the Adding Keys procedure on all keys or instruct the customer how to perform the Adding Keys procedure. Refer to Adding Keys .

Replace the theft deterrent control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 8

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8

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK