A/C Signal Circuit Troubleshooting (Climate Control System)

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 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: The A/C condenser fan, the radiator fan, or the A/C compressor, or if the heater is inoperative. Refer to the symptom troubleshooting. Symptom Related Diagnostic Procedures
- Before doing symptom troubleshooting, check for PGM-FI DTCs Initial Inspection and Diagnostic Overview.

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 B1241.

3. Do the sensor input display mode.

Is Sensor #5 (evaporator outlet air temperature) above 3 °C?

YES -

Go to step 4.

NO -

Go to step 9.

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

5. Disconnect climate control unit connector A (28P).

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

7. Measure the voltage between climate control unit connector A (28P) terminal No. 22 and body ground.





Is there battery voltage?

YES -

Replace the climate control unit; with navigation Climate Control Unit Removal/Installation (With Navigation), without navigation Climate Control Unit Removal/Installation (Without Navigation).

NO -

Go to step 8.

8. Measure the voltage between driver's under-dash fuse/relay box connector F (33P) terminal No. 22 and body ground.





Is there battery voltage?

YES -

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

NO -

Check for loose wires or poor connections at driver's under-dash fuse/relay box connector F (33P). 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, Canada models Drivers Under-dash Fuse/Relay Box (Drivers MICU) Removal and Installation (Canada models).

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

10. Disconnect climate control unit connectors A (28P) and B (12P).

11. Measure the evaporator temperature sensor resistance between climate control unit connector A (28P) terminal No. 20 and connector B (12P) terminal No. 9.





Is the resistance less than 24 kOhms?

YES -

Check for loose wires or poor connections at the 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; with navigation Climate Control Unit Removal/Installation (With Navigation), without navigation Climate Control Unit Removal/Installation (Without Navigation).

NO -

Go to step 12.

12. Disconnect the evaporator temperature sensor 2P connector.

13. Check for continuity between climate control unit connector A (28P) terminal No. 20 and evaporator temperature sensor 2P connector terminal No. 1.





Is there continuity?

YES -

Go to step 14.

NO -

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

14. Check for continuity between climate control unit connector B (12P) terminal No. 9 and evaporator temperature sensor 2P connector terminal No. 2.





Is there continuity?

YES -

Test the evaporator temperature sensor Testing and Inspection.

NO -

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