GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 236/246-NP8 (Two Speed Automatic) 🢒 Diagnostic System Check - HVAC Systems - Automatic

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 the HVAC Control Module, Body Control Module or Powertrain Control Module have set DTC's which may affect HVAC operation are present.

    3.

  3. The presence of DTCs which begin with "U", except U1500, indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed. Be sure to diagnose all other "U" codes before diagnosing a U1500.

    4.

  4. Answer Yes if the first three characters of the DTC name begins with B10; regardless of the last two characters.

Step

Action

Yes

No

1

Did you review A Diagnostic Starting Point - Heating, Ventilation and Air Conditioning?

Go to Step 2

Go to Diagnostic Starting Point - Heating, Ventilation and Air Conditioning in Heating, Ventilation and Air Conditioning

2

Install a scan tool.

Does the scan tool power up?

Go to Step 3

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

3

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the following control modules:
    3. • HVAC Control Module
    • Body Control Module
    • Powertrain Control Module

Does the scan tool communicate with the control modules?

Go to Step 4

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

4

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

  1. HVAC Control Module
  2. Body Control Module
  3. Powertrain Control Module

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - HVAC Systems - Automatic

5

Does the scan tool display any DTCs which begin with a "U", except U1500?

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

Go to Step 6

6

Does the scan tool display DTC B10XX?

Go to Diagnostic Trouble Code (DTC) List in Body Control Systems

Go to Step 7

7

Does the scan tool display any DTCs which begin with a B that are associated with the charging system?

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

Go to Step 8

8

Does the scan tool display U1500 or any DTCs that are associated with the HVAC system?

Go to Diagnostic Trouble Code (DTC) List

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 4.3 L or Diagnostic Trouble Code (DTC) List in Engine Controls - 4.8 L, 5.3 L, and 6.0 L or Diagnostic Trouble Code (DTC) List in Engine Controls - 8.1 L