GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The theft deterrent system function has been incorporated into the body control module (BCM).The theft deterrent is provided in order to prevent the vehicle operation if the correct key is not used in order to start the vehicle. The ignition key turns the lock cylinder. The cylinder rotation produces an analog voltage code in the Passlock sensor. Thi voltage code is received by the BCM. The BCM compares the voltage code to the previously learned voltage code. If the codes match, a class 2 message is sent from the BCM to the powertrain control module (PCM)/vehicle control module (VCM). The message enables the fuel injectors.

Diagnostic Aids

You must diagnose the diagnostic trouble codes (DTCs) in the order specified in the Passlock™ system DTC list. Failure to do so may result in the following conditions:

    • Extended diagnostic time
    • Incorrect diagnosis
    • Incorrect parts replacement

If the BCM, the Passlock sensor, or the PCM/VCM have been replaced, perform the learn procedure before following the diagnostic system check.

Refer to the instrument panel section for additional information on the message center dispaly. Vehicles equipped with a content theft deterrent system use the message center in order to provide an indication similar to that of the vehicle theft deterrent system. Carefully follow the steps within the VTD Diagnostic System Check

Test Description

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

  1. This test inspects for a malfunction related to the instrument panel cluster (IPC) preventing the SECURITY telltale bulb inspection. If this malfunction is due to an open GAUGES fuse, the SECURITY telltale will not turn ON and the engine will not run.

  2. The SECURITY telltale will turn ON and remain ON when the ignition switch is in the RUN position and a Passlock™ DTC is currently detected.

  3. This test inspects for a tamper condition. The engine will not run while the SECURITY telltale is flashing and the tamper timer is running. Refer to Tamper Timer in Scan Tool Data Definitions Scan Tool Data Definitions for more information.

  4. This test inspects for a malfunction that prevents communication between the IPC and the body control module (BCM). This condition causes the security telltale to remain ON when the ignition switch is turned to the OFF position.

  5. This operation of the SECURITY telltale indicates that Passlock™ DTCs exist. If the scan tool is operating properly and indicates that no Passlock™ DTCs exist, the BCM may be malfunctioning.

  6. This condition indicates an open in the Passlock™ sensor circuits. If the powertrain parameter VTD Fuel Disable displays ACTIVE during or immediately following cranking, the sensor circuits are also open. This condition is tested in the DTC B2958 diagnostic table. Refer to DTC B2958 Security System Sensor Data Circuit High DTC B2958 Security System Sensor Data Circuit High .

Step

Action

Value(s)

Yes

No

1

Turn the ignition switch to the RUN position.

Does the SECURITY telltale turn ON?

--

Go to Step 2

Refer to Instrument Cluster System Check in Instrument Panel, Gauges and Console

2

Does the SECURITY telltale turn ON and remain ON for more than 5 seconds?

--

Go to Step 5

Go to Step 3

3

Does the SECURITY telltale turn ON for 3 seconds, turn OFF briefly, and then flash ON and OFF?

--

Go to Step 5

Go to Step 4

4

Does the SECURITY telltale turn ON for 3 seconds, turn OFF for 2 seconds, then turn ON steady?

--

Go to Step 1

Go to Step 9

5

Connect a scan tool to the data link connector (DLC).

Does the scan tool power up?

--

Go to Step 7

Go to Step 6

6

  1. Refer to Scan Tool Does Not Communicate with Class 2 Data Line in Wiring Systems.
  2. Perform any repairs as necessary.

Are the repairs complete?

--

Go to Step 1

--

7

  1. Turn the ignition switch to the RUN position.
  2. Using the scan tool, inspect for Passlock™ DTCs.

Does the scan tool display No Communication with Vehicle?

--

Go to Step 6

Go to Step 8

8

Are any Passlock™ DTCs present?

--

Go to the applicable DTC table

Go to Step 1

9

  1. Connect a scan tool to the DLC.
  2. Monitor the scan tool parameter Passlock™ Code from the Passlock™ data list.

Does the scan tool display a value of OPEN for the Passlock™ code?

--

Go to DTC B2958 Security System Sensor Data Circuit High

Go to Step 10

10

Attempt to start the vehicle.

Does the engine crank fast enough in order to start the vehicle?

--

Go to Step 11

Refer to Starting System Check in Engine Electrical

11

Does the engine start and run?

--

System OK

Refer to:

Powertrain On Board Diagnostic (OBD) System Check

for 4.8L, 5.3L, and 6.0L engines.