Heating and A/C Systems Symptom Troubleshooting Index(Heating/Air Conditioning)

Symptom	Diagnostic Procedure	Also Check for
The blower and the heater controls and the A/C system do not work	Probable cause: HVAC control unit malfunction Do the HVAC control power and ground circuit troubleshooting	HVAC DTCs Blown fuse No. B22 (7.5 A) in the under-dash fuse/relay box Poor ground at G502 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 signal circuit malfunction Do the A/C signal circuit troubleshooting - Refer to: A/C Signal Circuit Troubleshooting(Idle Control System)A/C Signal Circuit Troubleshooting(Heating/Air Conditioning) A/C Signal Circuit Troubleshooting(Climate Control) Probable cause: A/C pressure sensor circuit malfunction or evaporator temperature sensor circuit malfunction Troubleshoot the A/C pressure sensor circuit: A/C pressure sensor circuit low voltage A/C pressure sensor circuit high voltage NOTE: The A/C pressure sensor circuit can malfunction without setting a DTC	HVAC DTCs PGM-FI DTCs - Refer to: How to Troubleshoot the Fuel and Emissions Systems How to Troubleshoot the CVT System(CVT System) Abnormal A/C system pressures Faulty evaporator temperature sensor Poor or loose connections at the terminals
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	HVAC DTCs PGM-FI DTCs - Refer to: How to Troubleshoot the Fuel and Emissions Systems How to Troubleshoot the CVT System(CVT System) Blown fuse No. A27 (7.5 A) in the under-hood fuse/relay box A/C thermal protector has continuity Poor or loose connections at the terminals
The A/C condenser/radiator fans do not run at low speed with the A/C on, but the blower and heater controls work normally	Probable cause: A/C condenser/radiator fan low speed circuit malfunction Do the radiator and A/C condenser fan low speed circuit troubleshooting - Refer to: A/C Condenser Fan High Speed Circuit Troubleshooting Radiator and A/C Condenser Fan Low Speed Circuit Troubleshooting	HVAC DTCs PGM-FI DTCs - Refer to: How to Troubleshoot the Fuel and Emissions Systems How to Troubleshoot the CVT System(CVT System) Blown fuse No. A2-11 (20 A) in the under-hood fuse/relay box Poor ground at G302 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 with the A/C on	Probable cause: Malfunction in the fan(s) high speed circuit Do the following troubleshooting as needed: A/C condenser fan high speed circuit troubleshooting - Refer to: A/C Condenser Fan High Speed Circuit Troubleshooting Radiator and A/C Condenser Fan Low Speed Circuit Troubleshooting Radiator fan high speed circuit troubleshooting - Refer to: Radiator and A/C Condenser Fan Low Speed Circuit Troubleshooting Radiator Fan High Speed Circuit Troubleshooting	HVAC DTCs PGM-FI DTCs - Refer to: How to Troubleshoot the Fuel and Emissions Systems How to Troubleshoot the CVT System(CVT System) Blown fuse No. A2-10 (20 A) and/or No. A8 (7.5 A) in the under-hood fuse/relay box Poor ground at G302 Poor or loose connections at the terminals

Symptom	Diagnostic Procedure	Also Check for
The A/C compressor clutch cycles rapidly on and off	Probable cause: A/C system is overcharged (Excessive pressure on high side of system causing pressure sensor to turn A/C compressor off) Radiator and/or A/C condenser fan inoperative Low idle speed	HVAC DTCs Faulty A/C pressure sensor
Insufficient heating (with heater)	1.Check the coolant level 2.Check the radiator cap 3. Check the engine coolant temperature (ECT) during normal operation with the HDS 4. 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 5.Do the air mix control motor test - Refer to: Passenger's Air Mix Control Motor Test Air Mix Control Motor Test 6. Check the blower motor unit for obstructions 7. Check for air leaks around the ducts and vents	HVAC DTCs