Symptom Troubleshooting Index

Symptom	Diagnostic procedure	Also check for
The rear mode control doors do not change between ceiling vents (cool) and floor vents (hot)	Probable cause: Rear mode control motor circuit malfunction. Do the rear mode control motor circuit troubleshooting (see REAR MODE CONTROL MOTOR CIRCUIT TROUBLESHOOTING )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Blown fuse No. 36 (10 A) in the under-dash fuse/relay box Poor or loose connections at the terminals
The blower and heater controls and the A/C system do not work	Probable cause: The HVAC control unit has malfunctioned, or has lost power or ground. Do the HVAC control power, ground, and communication circuit troubleshooting (see HVAC CONTROL POWER, GROUND, AND COMMUNICATION CIRCUIT TROUBLESHOOTING )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Blown fuse No. 36 (10 A) in the under-dash fuse/relay box Poor ground at G403 (see CONNECTOR TO FUSE/RELAY BOX INDEX ) Poor or loose connections at the terminals
The A/C compressor clutch and the A/C condenser/radiator fans are inoperative, but the blower and heater controls work	Probable cause: A/C pressure sensor circuit malfunction. NOTE: The A/C pressure sensor can malfunction without setting a DTC	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Poor or loose connections at the terminals A/C signal circuit problem in the PCM (see A/C SIGNAL CIRCUIT TROUBLESHOOTING )
The A/C compressor clutch does not engage, but the A/C condenser/radiator fans operate, and the blower and heater controls work	Probable cause: No power to the A/C compressor clutch. Do the A/C compressor clutch circuit troubleshooting (see A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTING ) Low speed idle High engine coolant temperature (ECT) Do the evaporator temperature sensor test (see EVAPORATOR TEMPERATURE SENSOR TEST )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 20 (7.5 A) in the under-hood fuse/relay box A/C system pressure is normal (see A/C PRESSURE SENSOR ) Poor or loose connections at the terminals
The A/C condenser fan and/or the radiator fan do not run with the A/C on	Probable cause: A/C condenser/radiator fan low speed circuit malfunction. Do the radiator and A/C condenser fan low speed circuit troubleshooting (see RADIATOR AND A/C CONDENSER FAN LOW SPEED CIRCUIT TROUBLESHOOTING )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 7 (30 A) Poor ground at G201 (see CONNECTOR TO FUSE/RELAY BOX INDEX ) Poor or loose connections at the terminals
The A/C condenser/radiator fans do not run at high speed, but do run at low speed	Probable cause: Malfunction in the fan high speed circuit(s). Do the following troubleshooting as needed: A/C condenser fan high speed circuit troubleshooting (see A/C CONDENSER FAN HIGH SPEED CIRCUIT TROUBLESHOOTING ) Radiator fan high speed circuit troubleshooting (see RADIATOR FAN HIGH SPEED CIRCUIT TROUBLESHOOTING )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 7 (30 A) and No. 6 (30 A) Poor ground at G202 (see CONNECTOR TO FUSE/RELAY BOX INDEX ) Poor or loose connections at the terminals A/C pressure sensor malfunction Check A/C system pressure (see A/C SYSTEM TEST )
Blower fan runs slower than expected in cold weather (when in AUTO mode) NOTE: It is normal for the blower fan to run slowly until the coolant temperature rises when in AUTO mode	Probable cause: Engine coolant temperature (ECT) circuit malfunction. Troubleshoot the ECT sensor circuit: ECT sensor 2 circuit low voltage (see DTC P2184: ECT SENSOR 2 CIRCUIT LOW VOLTAGE ) ECT sensor 2 circuit high voltage (see DTC P2185: ECT SENSOR 2 CIRCUIT HIGH VOLTAGE )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Manual blower motor operation Engine thermostat
The A/C compressor clutch cycles rapidly on and off	Probable cause: A/C system is very low on refrigerant, indicating a possible leak. Do the refrigerant leak check (see REFRIGERANT LEAK CHECK ) and repair any leaks. Evaporator temperature sensor malfunction. Do the evaporator temperature sensor test (see EVAPORATOR TEMPERATURE SENSOR TEST )	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) If there is no leak and the refrigerant level is normal, do the A/C compressor clutch circuit troubleshooting (see A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTING ), and look for an intermittent problem
The A/C compressor clutch does not disengage when the A/C switch is off	Probable cause: The A/C compressor clutch circuit is on (energized) continuously, shorted to ground, stuck A/C compressor clutch relay, or the A/C compressor clutch is mechanically jammed Do the A/C compressor clutch circuit troubleshooting (see A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTING ), and repair any circuit problems If the A/C compressor clutch circuit is OK, then do the A/C compressor clutch check (see A/C COMPRESSOR CLUTCH CHECK ), and repair any problems with the A/C compressor clutch	The A/C compressor relief valve. If it has vented refrigerant to the atmosphere, correct the problem with the A/C compressor clutch or clutch circuit, then replace the relief valve (see A/C COMPRESSOR RELIEF VALVE REPLACEMENT )
The A/C compressor relief valve has vented refrigerant NOTE: This indicates the A/C system pressure was very high	Probable cause: A high-side restriction, the A/C condenser/radiator fans are inoperative, or the A/C compressor clutch is not disengaging If the fans and A/C compressor clutch operate normally, recover refrigerant (see REFRIGERANT RECOVERY ), and check for restrictions If the A/C compressor clutch will not disengage, troubleshoot the A/C compressor clutch circuit (see A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTING ), and check for mechanical problems (see A/C COMPRESSOR CLUTCH CHECK ) If the fans are inoperative, troubleshoot the fan circuits (see RADIATOR AND A/C CONDENSER FAN LOW SPEED CIRCUIT TROUBLESHOOTING )	Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION )
HDS does not communicate with the HVAC control unit or the vehicle	Troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING )
Insufficient heating	Check the coolant level (see COOLANT CHECK ) Check the radiator cap (see RADIATOR CAP TEST ) Check the coolant temperature during normal operation Check the heater core inlet hose temperature: If it is COLD, check for restrictions in the hose, a damaged or leaking thermostat, or a damaged or leaking water pump If it is HOT, check for restrictions in the heater core. Back flush or replace the heater core Check the operation of the air mix door (see FRONT AIR MIX CONTROL MOTOR TEST ) Check the blower motor unit for obstructions Check for air leaks around the ducts and vents	HVAC DTCs (see HOW TO CHECK FOR DTCS WITH THE HDS ) Damaged cylinder head gasket