GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Diagnostic System Check

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. Determine if HVAC, Body Control Module, or Powertrain Control Module DTCs which may affect HVAC operation are present.

    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

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 systems:
    3. • The HVAC control assembly
    • The body control module
    • The powertrain control module

Does the scan tool communicate with these systems?

Go to Step 3

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

3

  1. Select the HVAC control assembly display DTCs function on the scan tool.
  2. Select the body control module display DTCs function on the scan tool.
  3. Select the powertrain control module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 4

Go to Symptoms

4

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

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

Go to DTC Table