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HVAC System - Automatic: Diagnosis GMC Envoy I

Automatic HVAC System ~698 words

A/C-HEATER CONTROL MODULE DIAGNOSTIC SYSTEM CHECK

  1. Install scan tool. Turn ignition switch to RUN position. Check for A/C-heater system DTCs. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-40623-S12217572702001011200000) under TESTING. If scan tool communicates with vehicle, go to step 19). If scan tool does not communicate with vehicle, go to next step.
  2. If A/C-heater control module does not operate and there is no scan tool data, go to next step. If A/C-heater control module operates but there is no scan tool data, go to step 21).
  3. Turn radio on. If radio has power, go to next step. If radio has no power, go to step 10).
  4. Check HVAC fuse. If fuse is okay, go to next step. If fuse is not okay, go to step 15).
  5. Using a Digital Volt-Ohmmeter (DVOM), backprobe A/C-heater control module connector terminal C12 (Orange wire). If DVOM indicates battery voltage, go to next step. If DVOM indicates other than battery voltage, go to step 9).
  6. Turn ignition to ON position. Using a DVOM, backprobe A/C-heater control module connector terminal C6 (Brown wire). If DVOM indicates battery voltage, go to next step. If DVOM indicates other than battery voltage, go to step 8).
  7. Replace A/C-heater control module. Recheck A/C-heater control module functions for proper operation.
  8. Repair open in Brown wire between fuse block and terminal C6. Recheck A/C-heater control module functions for proper operation.
  9. Repair open in Orange wire between splice and terminal C12.
  10. Check RDO/BATT fuse. If fuse is okay, go to step 9). If fuse is not okay, go to next step.
  11. Connect test light between terminals "A" and "B" of RDO/BATT fuse (leave test light connected for remainder of test). If test light glows, go to next step. If test light does not glow, go to step 14).
  12. Disconnect A/C-heater control module connector. If test light remains on, go to next step. If test light goes out, go to step 7).
  13. Repair short to ground in Orange wire to A/C-heater control module terminal C12. Recheck A/C-heater control module functions for proper operation.
  14. Disconnect test light, replace RDO/BATT fuse. Recheck A/C-heater control module functions for proper operation. If problem continues, check for poor connections or intermittent operation.
  15. Connect test light between terminals "A" and "B" of HVAC fuse in instrument panel fuse block (leave test light connected for remainder of test). If test light comes on, go to next step. If test light does not come on, go to step 18).
  16. Disconnect A/C heater control module connector. If test light remains lit, go to next step. If test light goes out, go to next step.
  17. Repair short to ground between fuse block and terminal C6 of A/C-heater control module. Recheck A/C-heater control module functions for proper operation.
  18. Replace HVAC fuse. Recheck A/C-heater control module functions for proper operation. If problem continues, check for poor connections or intermittent operation
  19. Recheck for A/C-heater control module DTCs. If DTCs are present, go to next step. If there are no DTCs but a symptom exists, see «AIR DISTRIBUTION SYSTEM DOES NOT OPERATE PROPERLY»(ref-40623-S20461233592001011200000) or BLOWER MOTOR CONTROL DOES NOT OPERATE PROPERLY.
  20. Turn ignition switch to OFF position. Record DTCs. Diagnose and repair DTCs from lowest number to highest. See appropriate DTC for diagnosis and repair information under TESTING. A history DTC could indicate a problem has been repaired or is intermittent. Clear all DTCs, operate climate control system, recheck for DTCs. Diagnose and repair as needed.
  21. If scan tool will not communicate with vehicle or no data is displayed, see TESTS W/CODES article in ENGINE PERFORMANCE. If symptom is other than no communication with scan tool, go to step 19).

TESTING

WARNINGTo avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG RESTRAINT SYSTEM article in ACCESSORIES AND ELECTRICAL.

Note. For testing procedures not covered in this article, see A/C-HEATER SYSTEM - MANUAL article.

RETRIEVING DIAGNOSTIC TROUBLE CODES

Diagnostic Trouble Codes (DTCs) can only be retrieved using a scan tool. To do so, install scan tool. Retrieve and record current and history DTCs. Proceed to appropriate DTC, follow diagnostic and repair procedures.

CLEARING TROUBLE CODES

Current DTCs will clear as soon as fault in system goes away or is repaired. History DTCs can only be cleared by disconnecting negative battery cable, or by using a scan tool to manually clear history codes.

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