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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Body and Accessories 🢒 Theft Deterrent 🢒 Diagnostic System Check - Theft Deterrent

Diagnostic Aids

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

    • Extended diagnostic time
    • Incorrect diagnosis
    • Incorrect parts replacement

If the Passlock module , the Passlock™ sensor, or the PCM 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 display. 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 Theft Deterrent Diagnostic System Check.

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. 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.

    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.

Step

Action

Yes

No

Schematic Reference: Theft Deterrent System Schematics

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 modules:
    3. • Passlock Module
    • Passlock Module

Does the scan tool communicate with the modules?

Go to Step 3

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

3

Select all DTC's display function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 5

Go to Step 4

4

  1. Momentarily rotate the ignition switch to the CRANK position. Do not start the engine.
  2. Release the ignition switch to the ON position.
  3. With a scan tool, observe the Passlock code in the Passlock module data list.

Does the scan tool display open?

Go to DTC B2958

Go to Symptoms - Theft Deterrent

5

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 Diagnostic Trouble Code (DTC) List