GM Service Manual Online
For 1990-2009 cars only

Object Number: 381660  Size: LF
Theft Deterrent System Components
Theft Deterrent System Schematics
Handling ESD Sensitive Parts Notice

Circuit Description

The body control module (BCM) will read an analog voltage form the Passlock sensor. Based on an internal reference, the BCM will determine if the measured voltage is in 1 of the following conditions:

    • Open
    • Shorted to ground
    • A valid code
    • A tamper code

There are 10 possible valid code combination. The BCM will only recognize the last learned valid code.

Conditions for Setting the DTC

    • The BCM will inspect for a valid code when the ignition is rotated from ON to CRANK and will continue to monitor the signal during the engine running period.
    • The BCM is reading a valid but different code value than previously learned form the Passlock sensor.

Action Taken When the DTC Sets

    • The vehicle will not start if the fault occurs before you start the vehicle. The security telltale will be FLASHING.
    • If the vehicle is running when the fault occurs, the BCM will be in the fail enable mode allowing the vehicle to start and run. The security indicator will be on.

Conditions for Clearing the DTC

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

Diagnostic Aids

    • When replacing the Passlock sensor, all of the following components are included as a replacement part and must be replaced:
       - The lock
       - The sensor
       - The filter
       - The harness
    • Use a scan tool in order to inspect the Passlock data voltage and the Passlock code.
    • Perform a visual inspection of the wiring and the connectors.
    • Inspect the Passlock sensor harness for an intermittent or a short to battery. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. If the Passlock sensor has been replaced without the Theft Relearn Procedure, DTC B2960 will set.

  2. This step will determine if there is a leakage path in the Passlock sensor which would cause the Passlock code voltage to drop.

Step

Action

Value(s)

Yes

No

1

Did you perform the Vehicle Theft Deterrent (VTD) System Check?

--

Go to Step 2

Go to Vehicle Theft Deterrent (VTD) System Check

2

Did you just replace the Passlockā„¢ sensor?

--

Go to Step 6

Go to Step 3

3

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the BCM connector C2. Refer to Theft Deterrent System Components
  3. Use a J 39200 digital multimeter (DMM) in order to measure the resistance between the BCM connector C2 terminal A2 and B3.
  4. Allow the meter reading to stabilize.

Does the scan tool indicate the specified value?

Is the resistance within the specified range?

Less than 1000ohms

Go to Step 4

Go to Step 5

4

Replace the BCM. Refer to Body Control Module Replacement in Body Control Systems.

Is the repair complete?

--

Go to Step 6

--

5

  1. Replace the Passlock sensor. Refer to Theft Deterrent System Components
  2. Perform the Theft Relearn Procedure. Refer to PASSLOCK Reprogramming Auto Learn .

Is the repair complete?

--

Go to Step 6

--

6

  1. Reconnect all of the previously disconnected connectors and the components.
  2. Turn the ignition switch to the ON position.
  3. Connect the scan tool.
  4. Clear the DTCs.
  5. Perform the Theft Relearn Procedure. Refer to PASSLOCK Reprogramming Auto Learn .

Is the operation complete?

--

Go to Vehicle Theft Deterrent (VTD) System Check

--