Manual Heating Ventilation Air Conditioning Systems Diagnostic System Check

NOTE: The presence of DTCs which begin with "U" indicate some other module on class 2 serial data line is not communicating.

After reviewing DESCRIPTION & OPERATION in appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Go to next step.
Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST A: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS.
Turn ignition switch to RUN position. Using scan tool, attempt to communicate with Powertrain Control Module (PCM). If scan tool communicates with PCM, go to next step. If scan tool does not communicate with PCM, go to TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
Using scan tool, select DISPLAY DTCS function. Retrieve and record any PCM DTCs and their status. If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair HEATING VENTILATION AIR CONDITIONING (HVAC) concern by symptom. See appropriate A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
If scan tool does not display any DTCs which begin with a "U", go to next step. If scan tool displays any DTCs which begin with a "U", go to TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
If scan tool displays any DTCs which begin with a "P" that are associated with the HVAC system, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool displays any DTCs which begin with a "P" that are not associated with the HVAC system, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.