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Test M: System Does Not Maintain Set Temperature

WARNING: This page is about a different car, the 2002 Buick LeSabre. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: For circuit reference, see CONNECTOR IDENTIFICATION  and/or WIRING DIAGRAMS  .
  1. Did you perform the Diagnostic System Check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Install scan tool. Turn ignition on. Using scan tool, perform RECALIBRATE ALL MOTORS command in instrument panel module special functions. Using scan tool, observe current DTC list in IPM data list. If scan tool displays any DTCS, go to DIAGNOSTIC TROUBLE CODE IDENTIFICATION  table under SELF-DIAGNOSTIC SYSTEM. If scan tool does not display any DTCs, go to next step.
  3. Inspect for a poor battery condition. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. Repair as necessary, then go to step  22. If battery is okay, go to next step.
  4. Visually inspect HVAC control module, steering wheel controls and personalization controls for stuck or intermittent sticking switches. Repair as necessary, then go to step  22. If switches are okay, go to next step.
  5. Ensure customer is using correct key to enable personalization and is not inadvertently activating steering wheel controls or right air temperature switch assembly. If correct key is being used, go to next step.
  6. Install scan tool. Cover sunload sensor assembly. Start engine. Place temperature switch to 75°F (24°C) position. Place right air temperature switch assembly to neutral. Using scan tool, observe RIGHT and LEFT SOLAR SENSOR data parameters in IPM open/short data list. If scan tool indicates both right and left solar sensor parameters are greater than 224 counts, go to next step. If scan tool indicates both right and left solar sensor parameters are less than 224 counts, go to step  17.
  7. Uncover sunload sensor assembly. Direct a light source at right and left sides of sunload sensor. If counts change similarly and correspond to proper side of sunload sensor, go to next step. If counts do not change, go to step  17.
  8. Fully open all panel outlets. Place temperature switch to 75°F (24°C) position. Place mode switch in PANEL position. Set blower speed to illuminate 2 bars on blower speed display. Place right air temperature switch assembly to neutral. Check for airflow through inside air temperature sensor by placing a 2" square piece of paper over sensor air inlet. If paper stays in place, go to next step. If paper does not stay in place, go to step  16.
  9. Turn ignition off. Check right and left panel and heater temperature sensors for correct installation. Repair installation as necessary, then go to step  22. If installation is correct, go to next step.
  10. Check fright and left panel and heater temperature sensor harness connectors or poor connections. Repair connections as necessary, then go to step  22. If connections are okay, go to next step.
  11. Check temperature sensor resistances. If resistances are to specification, go to next step. If resistances are not to specification, go to step  21.
  12. Check ambient air temperature sensor for poor connections. Repair as necessary, then go to step  22. If connections are okay, go to next step.
  13. Check ambient air temperature sensor resistance. See Figure. If resistances are to specification, go to next step. If resistances are not to specification, go to step  19.
  14. Check inside air temperature sensor for poor connections. Repair as necessary, then go to step  22. If connections are okay, go to next step.
  15. Check inside air temperature sensor resistance. See Figure. If resistances are to specification, system is okay. If resistances are not to specification, go to step  20.
  16. Check for a blocked or disconnected aspiration hose. Repair as necessary, then go to step  22.
  17. Check for correct orientation and poor connection at sunload sensor assembly. Repair as necessary, then go to step  22. If sunload sensor is okay, go to next step.
  18. Replace sunload sensor assembly. See SUNLOAD SENSOR  under REMOVAL & INSTALLATION. After repairs are complete, go to step  22.
  19. Replace ambient air temperature sensor. See AIR TEMPERATURE SENSORS  under REMOVAL & INSTALLATION. After repairs are complete, go to step  22.
  20. Replace inside air temperature sensor. See AIR TEMPERATURE SENSORS  under REMOVAL & INSTALLATION. After repairs are complete, go to step  22.
  21. Replace suspect air temperature sensor. See AIR TEMPERATURE SENSORS  under REMOVAL & INSTALLATION. After repairs are complete, go to next step.
  22. Start engine. Operate system to verify repair. If system operates properly, system is okay. If system does not operate properly, go to step  2.
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