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Radiator Fan High Speed Circuit Troubleshooting

WARNING: This page is about a different car, the 2011 Honda Pilot, 2010 Honda Pilot, and 2009 Honda Pilot. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check the No. 7 (30 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 fuse(s) OK? 

    YES  - Reinstall the fuse(s), then go to step  2.

    NO-Replace the fuse. 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, and the under-dash fuse/relay box and the under hood fuse/relay box. ■

  2. Remove the radiator fan relay and the fan control relay from the under-hood fuse/relay box, and test them (see 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 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. ■

    Fig 1: Checking Voltage Between Radiator Fan Relay 4P Socket Terminal No. 1 & Body Ground
    G05961203Courtesy of AMERICAN HONDA MOTOR CO., INC.
  4. Connect fan control relay 5P socket terminals No. 1 and No. 2 with a jumper wire.
    Fig 2: Connecting Fan Control Relay 5P Socket Terminals No. 1 & No. 2 With Jumper Wire
    G05961204Courtesy of AMERICAN HONDA MOTOR CO., INC.
  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.

    Fig 3: Connecting Radiator Fan Relay 4P Socket Terminals No. 1 & No. 2 With Jumper Wire
    G05961205Courtesy of AMERICAN HONDA MOTOR CO., INC.
  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. ■

    Fig 4: Checking Continuity Between Fan Control Relay 5P Socket Terminal No. 2 & Body Ground
    G05961206Courtesy of AMERICAN HONDA MOTOR CO., INC.
  7. Test the radiator fan motor (see FAN MOTOR TEST ).

    Is the motor OK? 

    YES  - Go to step  8.

    NO  - Replace the radiator fan motor (see RADIATOR AND FAN REPLACEMENT ).

  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. ■

    Fig 5: Checking Continuity Between Radiator Fan Relay 4P Socket Terminal No. 2 & Radiator Fan Motor 2P Connector Terminal No. 2
    G05961207Courtesy of AMERICAN HONDA MOTOR CO., INC.
  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 and the radiator fan motor, the under-hood fuse/relay box and body ground (G202). ■

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

    Fig 6: Checking Continuity Between Fan Control Relay 5P Socket Terminal No. 1 & Radiator Fan Motor 2P Connector Terminal No. 1
    G05961208Courtesy of AMERICAN HONDA MOTOR CO., INC.
  10. Turn the ignition switch to ON (II).
  11. Measure the voltage between fan control relay 5P socket terminal No. 5 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. ■

    Fig 7: Checking Voltage Between Fan Control Relay 5P Socket Terminal No. 5 & Body Ground
    G05961209Courtesy of AMERICAN HONDA MOTOR CO., INC.
  12. Turn the ignition switch to LOCK (0).
  13. Connect the Honda Diagnostic System (HDS) to the data link connector (DLC).
  14. Turn the ignition switch to ON (II).
  15. Make sure the HDS communicates with the vehicle and the powertrain control module (PCM). If it does not communicate, troubleshoot the DLC circuit.
  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 PCM from damage.
  17. Disconnect PCM connector A (49P).
  18. Check for continuity between fan control relay 5P socket terminal No. 3 and PCM connector terminal A5.

    Is there continuity? 

    YES  - Update the PCM (see PCM UPDATE ) if it does not have the latest software, or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ). ■

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

    Fig 8: Checking Continuity Between Fan Control Relay 5P Socket Terminal No. 3 & PCM Connector Terminal A5
    G05961210Courtesy of AMERICAN HONDA MOTOR CO., INC.
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