A/C Signal Circuit Troubleshooting
NOTE:
  • If the blower motor does not run at all speeds, the A/C compressor will be inoperative. Run the self-diagnostic function, and check the DTC B1241. Before performing any other troubleshooting, repair the cause of the inoperative blower motor.
  • Do not use this troubleshooting procedure if any of the following items are operative; condenser fan, radiator fan, A/C compressor, or if the heater is inoperative. Refer to the symptom troubleshooting index.
  • Before doing symptom troubleshooting, check for powertrain DTCs, R20A3 engine model, K24Z3 engine model. Also check for B-CAN codes.
  1. Turn the ignition switch to ON (II).
  1. Check if the blower motor operates at all speeds.
Does the blower motor operate at all speeds?
YES -
Go to Step 3 .
NO -
Repair the problem in the blower motor circuit.■
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect climate control unit connector A (28P).
  1. Turn the ignition switch to ON (II).
  1. Measure the voltage between climate control unit connector A (28P) No. 21 terminal and body ground.
Is there battery voltage?
YES -
Go to Step 7 .
NO -
Go to Step 8 .
  1. Measure the evaporator temperature sensor resistance between climate control unit connector A (28P) No. 23 terminal and connector B (12P) No. 10 terminal.
Is the resistance less than 24 kΩ?
YES -
Check for loose wires or poor connections at climate control unit connectors. If the connections are good, substitute a known-good climate control unit and recheck. If the symptom goes away, replace the original climate control unit .■
NO -
  1. Disconnect the A/C compressor 3P connector.
  1. Measure the voltage between the A/C compressor 3P connector No. 3 terminal (R20A3 engine model) or No. 2 terminal (K24Z3 engine model) and body ground.
Is there battery voltage?
YES -
Go to Step 10 .
NO -
Go to Step 12 .
  1. Turn the ignition switch to LOCK (0).
  1. R20A3 engine model: Measure the voltage between the A/C compressor 3P connector No. 1 and No. 3 terminals. K24Z3 engine model: Measure the voltage between the A/C compressor 3P connector No. 1 and No. 2 terminals.
Is there continuity?
YES -
Repair open in the wire between the A/C compressor and the climate control unit.■
NO -
Replace the thermal protector.■
  1. Measure the voltage between the driver's under-dash fuse/relay box connector F (33P) No. 5 terminal and body ground.
Is there battery voltage?
YES -
Repair open in the wire between the A/C compressor and the MICU.■
NO -
Check for loose wire or poor connections at driver's under-dash fuse/relay box connector F (33P) No. 5 terminal. If the connections are good, substitute a known-good MICU and recheck. If the symptom goes away, replace the original MICU .■