Heating/Air Conditioning Symptom Troubleshooting

Symptom Diagnostic procedure Also check for 
Recirculation control doors do not change between Fresh and Recirculate Recirculation control motor circuit troubleshooting 
  • HVAC DTCs
  • Blown fuse No. 36 (10 A) in the under-dash fuse/ relay box
  • Cleanliness and tightness of all terminals
 
Blower, heater controls, and A/C do not work HVAC control power and ground circuit troubleshooting 
  • HVAC DTCs
  • Blown fuse No. 36 (10 A) in the under-dash fuse/ relay box
  • Poor ground at G504
  • Cleanliness and tightness of all terminals
 
Both fans do not run at low speed with the A/C on (but the A/C compressor runs with the A/C on) Radiator and A/C condenser fan low speed circuit troubleshooting 
  • HVAC DTCs
  • Blown fuse No. 7 (20 A) (All M/T models and A/T model of K20Z2 engine) or (30 A) (A/T models except K20Z2 engine) in the under-hood fuse/relay box, and No. 36 (10 A) in the under-dash fuse/relay box
  • Poor ground at G301
  • Cleanliness and tightness of all terminals
 
The A/C condenser fan does not run at high speed (but both fans run at low speed and the A/C compressor operates with the A/C on) A/C condenser fan high speed circuit troubleshooting 
  • HVAC DTCs
  • Blown fuse No. 6 (20 A) and No. 15 (7.5 A) in the under-hood fuse/relay box
  • Poor ground at G301
  • Cleanliness and tightness of all terminals
 
Both fans do not run at high speed with the A/C on (but both fans run at low speed and the A/C compressor operates with the A/C on) A/C pressure sensor troubleshooting: A/C pressure sensor circuit low voltage, except K20Z2 engine, K20Z2 engine A/C pressure sensor circuit high voltage,except K20Z2 engine, K20Z2 engine
ECT troubleshooting: ECT sensor 2 circuit low voltage, except K20Z2 engine, K20Z2 engine, ECT sensor 2 circuit high voltage, except K20Z2 engine, K20Z2 engine 		 
The A/C compressor clutch does not engage (but both fans run with the A/C on) 1.

2. 		A/C compressor clutch circuit troubleshooting
A/C signal circuit troubleshooting 
  • HVAC DTCs
  • Blown fuse No. 12 (7.5 A) in the under-hood fuse/relay box, and No. 36 (10 A) in the under-dash fuse/relay box
  • Cleanliness and tightness of all terminals
 
A/C system does not come on (both fans and the A/C compressor do not work); heater is OK A/C pressure sensor troubleshooting: A/C pressure sensor circuit low voltage, except K20Z2 engine, K20Z2 engine A/C pressure sensor circuit high voltage, except K20Z2 engine, K20Z2 engine