Radiator Fan High Speed Circuit Troubleshooting

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Radiator Fan High Speed Circuit Troubleshooting

1. Fuse check:

-1. Check the following fuses.






Are the fuses OK?
-YES- The fuses are OK. Reinstall the fuses, then go to step 2.
-NO- Replace the fuse(s), and recheck. If the fuse(s) blows again, repair the short to ground on the No. A2-11 (20 A) fuse and No. B22 (7.5 A) fuse circuit.

2. Relay check:

-1. Check the following relays.






Are the relays OK?
-YES- The relays are OK. Go to step 3.
-NO- Replace the relay(s).

3. Determine possible failure area (under-hood fuse/relay box, fan control circuit):

-1. Measure the voltage between test points 1 and 2.










Is there battery voltage?
-YES- Go to step 4.
-NO- Replace the under-hood fuse/relay box Under-Hood Fuse/Relay Box Removal and Installation.

4. Determine possible failure area (GND line, others):

-1. Connect terminals A and B with a jumper wire.










-2. Connect terminals A and B with a jumper wire.










Does the radiator fan run at high speed?
-YES- Go to step 9.
-NO- Go to step 5.

5. Radiator fan motor operation check:

-1. Test the radiator fan motor Testing and Inspection.

Is the motor OK?
-YES- The radiator fan motor is OK. Go to step 6.
-NO- Replace the radiator fan motor Service and Repair.

6. Open wire check (GND line):

-1. Remove the jumper wires.

-2. Check for continuity between test points 1 and 2.










Is there continuity?
-YES- The GND wire is OK. Go to step 7.
-NO- Repair an open in the GND wire between the fan control relay 5P socket and the ground (G302).

7. Open wire check (MAIN FAN MOTOR line):

-1. Disconnect the flowing connector.






-2. Check for continuity between test points 1 and 2.










Is there continuity?
-YES- The MAIN FAN MOTOR wire is OK. Go to step 8.
-NO- Repair an open in the MAIN FAN MOTOR wire between the radiator fan relay 4P socket and the radiator fan motor 2P connector.

8. Open wire check (FAN HI/LO RLY COM line):

-1. Check for continuity between test points 1 and 2.










Is there continuity?
-YES- Check for poor connections or loose terminals at the under-hood fuse/relay box and the radiator fan motor.
-NO- Repair an open in the FAN HI/LO RLY COM wire between the fan control relay 5P socket and the radiator fan motor 2P connector.

9. Open wire check (MAIN FAN DIODE- line) 1:

-1. Remove the jumper wires.

-2. Turn the ignition switch to ON (II).

-3. Measure the voltage between test points 1 and 2.










Is there battery voltage?
-YES- The MAIN FAN DIODE- wire is OK. Go to step 10.
-NO- Repair an open in the MAIN FAN DIODE- wire between the radiator fan relay 4P socket and the under-dash fuse/relay box, or replace A/C diode B.

10. Open wire check (FAN LO SIGNAL- line):

-1. Turn the ignition switch to LOCK (0).

-2. Connect the HDS to the DLC How to Troubleshoot the Fuel And Emissions Systems.

-3. Turn the ignition switch to ON (II).

-4. Make sure the HDS communicates with the vehicle and the PCM. If it does not communicate, troubleshoot the DLC circuit Testing and Inspection.

-5. Turn the ignition switch to LOCK (0).

-6. Jump the SCS line with the HDS.
NOTE: This step must be done to protect the PCM from damage.

-7. Disconnect the following connector.






-8. Check for continuity between test points 1 and 2.










Is there continuity?
-YES- The FAN LO SIGNAL- wire is OK. Go to step 11.
-NO- Repair an open in the FAN LO SIGNAL- wire between the radiator fan relay 4P socket and the PCM.

11. Open wire check (MAIN FAN DIODE- line) 2:

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

-2. Measure the voltage between test points 1 and 2.










Is there battery voltage?
-YES- The MAIN FAN DIODE- wire is OK. Go to step 12.
-NO- Repair an open in the MAIN FAN DIODE- wire between the fan control relay 5P socket and the under-dash fuse/relay box.

12. Open wire check (FAN HI SIGNAL line):

-1. Turn the ignition switch to LOCK (0).

-2. Check for continuity between test points 1 and 2.










Is there continuity?
-YES- Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM Service and Repair, then recheck. If the PCM was substituted, and the symptom/indication goes away, replace the original PCM Service and Repair.
-NO- Repair an open in the FAN HI SIGNAL wire between the fan control relay 5P socket and the PCM.