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. The Passlock controller reads the coded Passlock data signal. The data consists of a voltage generated by a voltage divider network created between the Passlock assembly and the Passlock controller. If the data is correct , indicating rotation of the lock cylinder with the proper mechanically cut key, then the Passlock controller sends a password to the Powertrain controller via serial data to indicate that engine starting should be allowed. The Passlock controller also interfaces with the driver displays subsystem to indicate, via the security indicator, the Passlock subsystem's status and acute subsystem failures.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2960 Security System Sensor Data Incorrect but Valid

Conditions for Setting the DTC

    • The body control module (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 indicator 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

    • Use a scan tool in order to inspect the Passlock data voltage.
    • Inspect for poor connections at the Passlock sensor. Refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

  1. This step tests for the proper operation of the circuit in the normal voltage range.

Step

Action

Value(s)

Yes

No

Schematic Reference: Immobilizer Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Momentarily rotate the ignition switch to CRANK. Do not start the vehicle.
  3. Release the ignition switch to ON.
  4. Select the body control module (BCM) display DTCs function on the scan tool.

Does the scan tool display DTC B2960 as a current DTC?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

Does the scan tool display DTC B2957, B2958, or B3033?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 4

4

Have you replaced the Passlock sensor on this vehicle?

--

Go to Step 5

Go to Step 6

5

Have you performed a Passlock learn procedure after replacing the Passlock sensor?

--

Go to Step 6

Go to Step 9

6

With a scan tool, observe the Passlock data voltage for one minute.

Does the scan tool indicate that the Passlock data voltage is changing more than the specified value?

+/- 0.02 V

Go to Step 7

Go to Step 9

7

Inspect for poor connections at the Passlock sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

8

Replace the Passlock sensor. Refer to Ignition and Start Switch Replacement .

Did you complete the replacement?

--

Go to Step 9

--

9

Perform the Immobilizer System Component Programming procedure.

Is the repair complete?

--

Go to Step 10

--

10

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition.
  3. Momentarily rotate the ignition switch to CRANK. Do not start the vehicle.
  4. Release the ignition switch to ON.
  5. Select the body control module display DTCs function on the scan tool.

Does the DTC reset?

--

Go to Step 3

System OK