GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The Passlock™ system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate or the ignition switch is operated while separated from the ignition lock cylinder case. The body control module (BCM) provides security system sensor power and low reference for the Passlock™ sensor. The BCM also measures the security system sensor voltage.

When the correct key is used to start the vehicle, a magnet on the lock cylinder passes close to the Passlock™ sensor within the ignition lock cylinder case. The magnet activates the security hall effect sensor in the Passlock™ sensor which completes a circuit from the security sensor signal circuit through a resistor to the security sensor low reference circuit. The resistance value will vary from vehicle to vehicle. The BCM will measure the voltage on the security sensor signal circuit and compare this voltage to a previously learned voltage. If the voltage measured is within the valid range, the BCM will send a class 2 message to the powertrain control module (PCM) to enable vehicle starting. If the voltage measured is not within the valid range, a class 2 message will be sent to the PCM to disable starting of the vehicle.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3033 Security System Indicates Tamper

Conditions for Setting the DTC

    • The BCM will inspect for a tamper code when the ignition switch rotates from ON to CRANK and will continue to monitor the signal during the engine running period.
    • The BCM is reading a tamper code from the Passlock™ sensor for longer than one second.

Action Taken When the DTC Sets

    • The vehicle will not run. The SECURITY indicator will be flashing.
    • The Passlock™ state is tamper.

Conditions for Clearing the DTC

    • The DTC will clear once an ignition cycle occurs without the fault recurring.
    • The BCM history codes will clear after 100 ignition cycles occur without the fault recurring.
    • Use a scan tool

Diagnostic Aids

    • Prior to replacing a BCM, ensure that all of the diagnostics have been completed. Refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information.
    • Inspect the Passlock™ sensor harness for intermittent or poor connections. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • The vehicle theft deterrent (VTD) internal diagnostics are not run while the tamper timer is active.

Test Description

The number below refers to the step number on the diagnostic table:

  1. Tests for a magnetic field near the ignition lock cylinder.

Step

Action

Yes

No

Schematic Reference: Theft Deterrent System Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Important:: Do not start the vehicle.

  3. Momentarily rotate the ignition switch to CRANK.
  4. Release the ignition switch to ON.
  5. Select the body control module display DTCs function on the scan tool.

Does the scan tool display DTC B3033 as a current DTC?

Go to Step 3

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

3

Inspect the area around the ignition lock cylinder for any device which could create a magnetic field audio speaker, magnet, etc.

Is there a magnetic device near the ignition lock cylinder?

Go to Step 4

Go to Step 5

4

Remove the device creating the magnetic force.

Did you complete the repair?

Go to Step 8

--

5

Inspect for poor connections at the Passlock™ sensor. 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

6

Replace the Passlock™ sensor in the electronic column lock module assembly. Refer to Ignition Lock Cylinder Case Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 7

--

7

Perform the Programming Theft Deterrent System Components procedure.

Is the repair complete?

Go to Step 8

--

8

Important: You may have to wait up to 10 minutes in order to reset the body control module (BCM) and synchronize all of the Passlock™ components.

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition.
  3. Important: Do not start the vehicle.

  4. Momentarily rotate the ignition switch to CRANK.
  5. Release the ignition switch to ON.
  6. Select the body control module display DTCs function on the scan tool.

Does the DTC reset?

Go to Step 3

System OK