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

1. Turn ON the ignition, with the engine OFF.
2. Attempt to establish communication with the heater, the ECM, and A/C control unit.

Does the scan tool communicate with the heater and A/C control unit?

Go to Step 3

Go to Scan Tool Does Not Communicate with Keyword 82 Data Line in Data Link Communications

Select the Heating and Air Conditioning display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to DTC Table

Go to Symptoms