( TL19E00G24100000000HBAT00 )

Heating Symptom Troubleshooting Index

Symptom	Diagnostic procedure		Also check for
Blower and heater controls do not work	Heater control power and ground circuit troubleshooting		HVAC DTCs Blown fuse No. 16 (7.5 A) in the driver's under-dash fuse/relay box Poor ground at G401 Cleanliness and tightness of all terminals
Center display is not indicated	Audio communication line circuit troubleshooting		HVAC DTCs Cleanliness and tightness of all terminals
Blower fan runs slower than expected in cold weather	ECT troubleshooting: ECT sensor 2 circuit low voltage, R20A3 engine model, K24Z3 engine model: ECT sensor 2 circuit high voltage, R20A3 engine model, K24Z3 engine model NOTE: It is normal for the blower to run slowly until the engine coolant temperature begins to rise. If the blower continues to run slowly for an abnormal length of time, continue to troubleshoot the problem.		Powertrain DTCs, R20A3 engine model, K24Z3 engine model Blower motor operation
HDS does not communicate with the heater control unit or the vehicle	Troubleshoot the DLC circuit, R20A3 engine model, K24Z3 engine model
Insufficient heating	1. 2. 3. 4. 5. 6. 7.	Check the coolant level, R20A3 engine model, K24Z3 engine model Check the radiator cap; R20A3 engine model, K24Z3 engine model Check the operation of the air mix control motor and door Check the coolant temperature Check the blower motor unit for obstructions Check for air leaks around the ducts and vents Check the inlet hose temperature If it is COLD, check for restrictions in the hose, a damaged or leaking thermostat, and a damaged or leaking water pump. If it is HOT, check for restrictions in the heater core. Back flush the heater core using standard commercially available equipment, or replace the heater core.	Damaged cylinder head gasket