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HVAC Diagnostic System Check

  1. Verify operation of A/C-heater system. If A/C-heater system operates properly, go to next step. If A/C-heater system does not operate properly, repair as necessary. See appropriate A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  2. Connect scan tool. Turn ignition on. 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 in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  3. Turn ignition on. Attempt to establish communication with HVAC control module, Body Control Module (BCM) and Powertrain Control Module (PCM). If scan tool communicates with these control modules, go to next step. If scan tool does not communicate with these control modules, go to TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
  4. Display DTCs for HVAC control module, BCM and PCM. If scan tool displays any DTCs for these modules, go to next step. If scan tool does not display any DTCs for these modules, diagnose A/C-heater system by symptom. See appropriate A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  5. If scan tool displays any DTCs that begin with "U", go to TEST A: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display any DTCs that begin with "U", go to next step.
  6. If scan tool displays DTC B10XX, go to SELF-DIAGNOSTIC SYSTEM in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If scan tool does not display DTC B10XX, go to next step.
  7. If scan tool displays any DTCs that begin with "B" that are associated with the charging system, go to appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If scan tool does not display any DTCs that begin with "B" that are associated with the charging system, go to next step.
  8. If scan tool displays any DTCs associated with HVAC system, go to appropriate A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. If scan tool does not display any DTCs associated with HVAC system, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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