GM Service Manual Online
For 1990-2009 cars only

Object Number: 491232  Size: MF
Theft Deterrent System Components
Theft Deterrent Passlock ™ Lock Cylinder

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 one of the following conditions:

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

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

Conditions for Running the DTC

The ignition switch is cycled to ON.

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 from the Passlock sensor.

Action Taken When the DTC Sets

    • If the DTC sets during cranking, the car will not start or will start with the theft indicator illuminated.
    • If the DTC sets while the engine is running, the car will start on future attempts and the theft indicator is illuminated.
    • The SERVICE VEHICLE SOON indicator illuminates.

Conditions for Clearing the DTC

    • Current DTCs will clear after one ignition cycle if the malfunction is no longer present.
    • All of the BCM history codes will be cleared after 100 ignition cycles (from OFF to ON) with no current codes active during the 100 ignition cycles.

Diagnostic Aids

    • This DTC will not set if the BCM is in learn mode.
    • Inspect for a poor connection at the Passlock® sensor and BCM.
    • If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while wiggling the wiring and connectors. This will cause the malfunction to appear.

Test Description

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

  1. Tests for the proper operation of the circuit in the normal voltage range.

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Diagnostic System Check - Theft Deterrent

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 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 in Wiring Systems

3

Does the scan tool display DTC B2947, B2948, B2957, or B2958?

--

Go to Diagnostic Trouble Code (DTC) List/Type

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?

+/- 0.02v

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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

8

Replace the Passlock™ sensor. Refer to Ignition Lock Cylinder Replacement - On Vehicle in Steering Wheel and Column.

Did you complete the replacement?

--

Go to Step 9

--

9

Perform the Passlock™ learn procedure. Refer to Programming Replacement Lock Cylinder, Body Control Module or Powertrain Control Module .

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