Climate Control Symptom Troubleshooting

Symptom Diagnostic procedure Also check for 
Blower, heater controls, and A/C do not work Climate 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, 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. 20 (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  
Blower fan runs slower than expected in cold weather ECT troubleshooting: ECT sensor 2 circuit low voltage, except K20Z2 engine, K20Z2 engine, ECT sensor 2 circuit high voltage, except K20Z2 engine, K20Z2 engine
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 		 
HDS does not communicate with the climate control unit or the vehicle Troubleshoot the DLC circuit, except K20Z2 engine, K20Z2 engine