A/C Signal Circuit Troubleshooting (Without Climate Control)

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 for DTC 12. 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: The A/C condenser fan, the radiator fan, or the A/C compressor, or if the heater is inoperative. Refer to the symptom troubleshooting index.
- Before doing symptom troubleshooting, check for powertrain DTCs Initial Inspection and Diagnostic Overview. Also check for B-CAN codes.

1. Turn the ignition switch to ON (II).

2. 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 12.�

3. Turn the ignition switch to LOCK (0).

4. Disconnect the HVAC control unit 24P connector.

5. Turn the ignition switch to ON (II).

6. Measure the voltage between HVAC control unit 24P connector terminal No. 21 and body ground.





Is there battery voltage?

YES -

Go to step 8.

NO -

Go to step 7.

7. Measure the voltage between driver's under-dash fuse/relay box connector F (33P) terminal No. 5 and body ground.





Is there battery voltage?

YES -

Repair an open in the wire between the HVAC control unit and the driver's MICU.�

NO -

Check for loose wire or poor connections at driver's under-dash fuse/relay box connector F (33P) terminal No. 5. If the connections are good, substitute a known-good driver's under-dash fuse/relay box (includes the driver's MICU) and recheck. If the symptom goes away, replace the original driver's under-dash fuse/relay box (includes the driver's MICU); USA models Drivers Under-Dash Fuse/Relay Box (Drivers MICU) Removal And Installation (USA models), Canada models Drivers Under-Dash Fuse/Relay Box (Drivers MICU) Removal And Installation (Canada models).�

8. Turn the ignition switch to LOCK (0).

9. Measure the evaporator temperature sensor resistance between HVAC control unit 24P connector terminals No. 14 and No. 15.





Is resistance less than 24 kOhms?

YES -

Check for loose wires or poor connections at the HVAC control unit 24P connector. If the connections are good, substitute a known-good HVAC control unit and recheck. If the symptom goes away, replace the original HVAC control unit.�

NO -

Go to step 10.

10. Disconnect the evaporator temperature sensor 2P connector.

11. Check for continuity between HVAC control unit connector terminal No. 14 and evaporator temperature sensor 2P connector terminal No. 2.





Is there continuity?

YES -

Go to step 12.

NO -

Repair an open in the wire between the HVAC control unit and the evaporator temperature sensor.�

12. Check for continuity between HVAC control unit connector terminal No. 15 and evaporator temperature sensor 2P connector terminal No. 1.





Is there continuity?

YES -

Test the evaporator temperature sensor Evaporator Temperature Sensor Test.�

NO -

Repair an open in the wire between the HVAC control unit and the evaporator temperature sensor.�