Radiator Fan High Speed Circuit Troubleshooting

Radiator Fan High Speed Circuit Troubleshooting

1. Check the No. 7 (20 A) fuse in the under-hood fuse/relay box and the No. 36 (10 A) fuse in the under-dash fuse/relay box.

Are the fuses OK?
YES - Reinstall the fuse(s), then go to step 2.

NO - Replace the fuse(s) and recheck. If the fuse continues to blow, locate and repair the short in the circuit between the under-hood fuse/relay box and the radiator fan motor, or between the under-dash fuse/relay box connector terminal G12, the under-hood fuse/relay box and the engine control module (ECM).


2. Remove the radiator fan relay and the fan control relay from the under-hood fuse/relay box, and test them. Power Relay Test

Are the relays OK?
YES - Go to step 3.

NO - Replace the radiator fan relay and/or fan control relay.


3. Measure the voltage between the radiator fan relay 4P socket terminal No. 1 and body ground.

Is there battery voltage?
YES - Go to step 4.

NO - Replace the under-hood fuse/relay box.






4. Connect fan control relay 5P socket terminals No. 1 and No. 2 with a jumper wire.






5. Connect radiator fan relay 4P socket terminals No. 1 and No. 2 with a jumper wire.

Does the radiator fan run at high speed?
YES - Go to step 10.

NO - Go to step 6.






6. Remove the jumper wires, then check for continuity between fan control relay 5P socket terminal No. 2 and body ground.

Is there continuity?
YES - Go to step 7.

NO - Repair open in the wire between fan control relay 5P socket terminal No. 2 and body ground.






7. Test the radiator fan motor. Testing and Inspection

Is the motor OK?
YES - Go to step 8.

NO - Replace the radiator fan motor. Service and Repair


8. Check for continuity between radiator fan relay 4P socket terminal No. 2 and radiator fan motor 2P connector terminal No. 2.

Is there continuity?
YES - Go to step 9.

NO - Repair open in the wire between radiator fan relay 4P socket terminal No. 2 and radiator fan motor 2P connector terminal No. 2.






9. Check for continuity between fan control relay 5P socket terminal No. 1 and radiator fan motor 2P connector terminal No. 1.

Is there continuity?
YES - Check for poor connections or loose terminals at the under-hood fuse/relay box, the radiator fan motor, and body ground (G301), then go to step 1.

NO - Repair open in the wire between fan control relay 5P socket terminal No. 1 and radiator fan motor 2P connector terminal No. 1.






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

11. Measure the voltage between radiator fan relay 4P socket terminal No. 3 and body ground.

Is there battery voltage?
YES - Go to step 12.

NO - Repair open in the wire between the under-dash fuse/relay box and the under-hood fuse/relay box.






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

13. Connect the Honda Diagnostic System (HDS) to the data link connector (DLC). Initial Inspection and Diagnostic Overview

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

15. Make sure the HDS communicates with the vehicle and the ECM. If it does not communicate, troubleshoot the DLC circuit. Testing and Inspection

16. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).
NOTE: This step must be done to protect the ECM from damage.

17. Disconnect ECM connector A (44P).

18. Check for continuity between radiator fan relay 4P socket terminal No. 4 and ECM connector terminal A4.

Is there continuity?
YES - Go to step 19.

NO - Repair open in the wire between radiator fan relay 4P socket terminal No. 4 and ECM connector terminal A4.






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

20. Measure the voltage between fan control relay 5P socket terminal No. 5 and body ground.

Is there battery voltage?
YES - Go to step 21.

NO - Repair open in the wire between the under-dash fuse/relay box and the under-hood fuse/relay box.






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

22. Check for continuity between fan control relay 5P socket terminal No. 3 and ECM connector terminal A5.

Is there continuity?
YES - Update the ECM ECM Update if it does not have the latest software, or substitute a known-good ECM, Initial Inspection and Diagnostic Overview then recheck. If the symptom goes away with a known-good ECM, replace the original ECM. Service and Repair

NO - Repair open in the wire between fan control relay 5P socket terminal No. 3 and ECM connector terminal A5.