Heater And A/C Programmer Module (HCM) System Check

2000 Buick Park Avenue Base, 3.8 KSECTION Heater And A/C Programmer Module (HCM) System Check
  1. Connect scan tool to Data Link Connector (DLC). If scan tool works, go to next step. If scan tool does not work, go to SCAN TOOL DOES NOT POWER UP .
  2. Check for communication with HCM, PCM and SBM. If scan tool communicates with all modules, go to next step. If communication is not possible with one or more modules, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 SERIAL DATA LINE .
  3. Check for DTCs from HCM, PCM and SBM. If any DTCs exist, go to next step. If no DTCs exist, diagnose and repair system by symptom. See AUTOMATIC A/C-HEATER SYSTEMS - PARK AVENUE article in AIR CONDITIONING & HEATING.
  4. If no "U" prefix DTCs exist, go to next step. If any "U" prefix DTCs exist, go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 SERIAL DATA LINE .
  5. For all other DTCs, see DTC IDENTIFICATION  table under SELF-DIAGNOSTICS.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.