GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 2WD 🢒 Body and Accessories 🢒 Theft Deterrent 🢒 Diagnostic System Check - Theft Deterrent

Test Description

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

  1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

    2.

  2. Tests for an open in the Passlock™ sensor signal circuit, which may not set a DTC B2955 under certain conditions.

    3.

  3. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

    4.

  4. The presence of DTC P0601, P0602, or P0604 indicates an internal fault in the PCM.

  5. The presence of DTC B1000 indicates an internal module fault.

    6.

  6. The Presence of DTC P0562, P0563, P0621 or P0622indicates a low or high voltage condition.

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up in Data Link Communications

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the following control modules:
    3. • The powertrain control module (PCM)
    • The body control module (BCM)
    • The instrument panel cluster (IPC)

Does the scan tool communicate with the all the listed control modules?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

3

Important: Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

  1. Access the Class 2 Power Mode parameter in the Diagnostic Circuit Check menu on the scan tool.

    2. Important: Insure that all ignition switch positions are observed including the OFF position.

  2. Rotate the ignition switch through all positions while observing the Class 2 Power Mode parameter.

Does the Class 2 Power Mode parameter reading match the ignition switch position for all switch positions?

Go to Step 4

Go to Power Mode Mismatch in Body Control System

4

Select the display DTCs function on the scan tool for the following control modules:

    • The powertrain control module (PCM)
    • The body control module (BCM)
    • The instrument panel cluster (IPC)

Does the scan tool display any DTCs?

Go to Step 6

Go to Step 5

5

  1. Do not start the vehicle. Momentarily rotate the ignition switch to CRANK
  2. Release the ignition switch to ON.
  3. With a scan tool, observe the Passlock Code in the Body Control Module Security Data list.

Does the scan tool display OPEN?

Go to B2955 DTC B2955

Go to Symptoms - Theft Deterrent

6

Does the scan tool display any DTCs which begin with a "U"?

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

Go to Step 7

7

Does the scan tool display DTC P0601, P0602 or P0604?

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 4.2 L

Go to Step 8

8

Does the scan tool display DTC B1000?

Go to DTC B1000 in Body Control System

Go to Step 9

9

Does the scan tool display DTC P0562, P0563, P0621 or P0622?

Go to Diagnostic Trouble Code (DTC) List in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List