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Tahoe / Yukon Service Manual

HVAC System Malfunction

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Aids Check the following mechanical fault sources: Air distribution box Air distribution hoses/air distribution ducts Reference Information Schematic Reference HVAC Schematics Connector End View Reference Master Electrical Component List Description and Operation Automatic HVAC Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Verify no DTCs are set ⇒ If any DTCs are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTCs are set
  2. Verify the front blower motor operates properly with the blower motor switch in each speed position. ⇒ If the front blower motor does not operate in each speed position Refer to Blower Motor Malfunction. ⇓ If the front blower motor operates properly in each speed position
  3. Verify the auxiliary blower motor operates properly with the blower motor switch in each speed position. ⇒ If the auxiliary blower motor does not operate in each speed position Refer to Auxiliary Blower Motor Malfunction. ⇓ If the auxiliary blower motor operates properly in each speed position
  4. Verify every HVAC door moves correctly when operating the appropriate control. ⇒ If any HVAC door does not move correctly 4.1. Inspect the HVAC door for any mechanical issues that may limit or prevent the air control door from moving smoothly or moving through its full range of travel. ⇒ If any mechanical issues are found, repair or replace as necessary. ⇓ If no mechanical issues are found 4.2. Replace the malfunctioning actuator. ⇓ If all HVAC doors move correctly
  5. Install the appropriate Air Conditioning Recharge Service Center. Ignition ON.
  6. Verify the high side pressure reading on the Air Conditioning Service Center is within 10% of the scan tool A/C High Side Pressure Sensor parameter. ⇒ If the reading is not within 10% Refer to DTC P0532 or P0533. ⇓ If the reading is within 10%
  7. Verify the A/C High Side Pressure Sensor parameter is between 269−2929 kPa (39−425 PSI). ⇒ If the reading is not between 269−2929 kPa (39−425 PSI) Refer to Air Conditioning (A/C) System Performance Test ⇓ If the reading is between 269−2929 kPa (39−425 PSI)
  8. Verify the A/C Evaporator Temperature Sensor parameter is within 10% of ambient temperature. ⇒ If not within 10% of ambient temperature Refer to DTC P0535, P0537, P0538, or P153B. ⇓ If within 10% of ambient temperature
  9. Verify the Sunload Sensor parameter changes while covering the B10B Sun Load Temperature and Ambient Light and Security Indicator Sensor with a shop towel or other suitable item. ⇒ If the Sunload Sensor parameter does not change Refer to DTC B10FA or B1141. ⇓ If the Sunload Sensor parameter changes
  10. Verify the scan tool parameters listed below are within 10% of actual conditions. Passenger Compartment Humidity Passenger Compartment Humidity Sensor Temperature Windshield Temperature ⇒ If not within 10% of actual conditions Replace the B160 Inside Air Moisture and Windshield Temperature Sensor. ⇓ If within 10% of actual conditions
  11. Engine ON, A/C system ON
  12. Verify cool air flows from the ducts with the temperature control in the coldest position. ⇒ If the air is not cool 12.1. Verify the Q2 AIr Conditioning Clutch is engaged. ⇒ If the Q2 AIr Conditioning Clutch is not engaged, refer to Air Conditioning Compressor Malfunction. ⇒ If the Q2 AIr Conditioning Clutch is engaged, refer to Air Conditioning (A/C) System Performance Test and DTC B2AEF or B2AF0-B2AF4. ⇓ If the air is cool
  13. Verify warm air flows from the ducts with the temperature control in the warmest position. ⇒ If the air is not warm Refer to Heating Performance Diagnostic. ⇓ If the air is warm
  14. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. HVAC Component Replacement Reference Control Module References for control module replacement, programming and setup