GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon - 2WD 🢒 Body and Accessories 🢒 Roof 🢒 Diagnostic System Check - Power Sunroof

Test Description

The number(s) below refer to the step number(s) 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. Determining if any DTCs are set. If no DTCs are set then proceed to the Symptoms.

  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 either of these DTCs will inhibit the operation of the sunroof. If no DTCs are set then proceed to the Symptoms.

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 Body Control Module (BCM).

Does the scan tool communicate with the BCM?

Go to Step 3

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

3

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 in the Diagnostic Circuit Check on the scan tool.
  2. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter.

Does the ignition switch 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 BCM display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Roof

5

Select the BCM display DTCs function on the scan tool.

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

Go to Diagnostic Trouble Code (DTC) List in Data Link Communications

Go to Step 6

6

Does the scan tool display DTC B1477, or B1478?

Go to Diagnostic Trouble Code (DTC) List in Retained Accessory Power

Go to Symptoms - Roof