For 1990-2009 cars

### 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. Determine if the Instrument Panel Integration Module, Body Control Module or Powertrain Control Module have set DTCs which may affect HVAC operation are present.

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. 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:

• | Instrument Panel Integration 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:

• | Instrument Panel Integration Module

• | Body Control Module

• | 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? | 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 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 - 3.0 L