The ECM controls the speed of the fan by controlling the current to the fan control solenoid. The fan control solenoid controls the displacement of the hydraulic pump that supplies pressurized oil to the fan motor. The fan control solenoid is controlled by a signal between 0.3 and 1.6 Amp. The fan pump defaults to maximum pressure and a diagnostic code is generated if no signal is sent to the solenoid.
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| Illustration 1 | g00853247 |
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Schematic | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the keyswitch to the OFF/RESET position.
- Thoroughly inspect the J1/P1 ECM connector and all other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Expected Result:
All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points. All connections and grounds should be tight and free of corrosion.
Results:
- OK - Proceed to Test Step 2.
- Not OK -
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
Test Step 2. Check the Resistance through the Solenoid
- Disconnect the J508/P508 fan control solenoid connector.
- Measure the resistance of the solenoid between J508:1 (Fan Control Solenoid) and J508:2 (Solenoid Return).
Expected Result:
Resistance should be between 40 and 45 Ohms.
Results:
- OK - Proceed to Test Step 4.
- Not OK - There may be a problem with the fan control solenoid. Proceed to Test Step 3.
Test Step 3. Temporarily Install a New Fan Control Solenoid
- Remove the fan control solenoid.
- Temporarily install a new fan control solenoid.
- Turn the keyswitch to the ON position.
- Clear any logged diagnostic codes.
- Start the engine.
- Check for diagnostic codes for the engine fan control solenoid on ET.
- Ensure that the engine fan control solenoid is working properly.
- Turn the keyswitch to the OFF/RESET position.
Expected Result:
The engine fan control solenoid should be working properly. There should be no active diagnostic codes for the engine fan control solenoid.
Results:
- OK - The fan control solenoid was faulty.
Repair: Permanently install the new fan control solenoid.
Verify that the repair eliminates the problem.
STOP
- Not OK - There may be a problem with the harness. Proceed to Test Step 4.
Test Step 4. Check for Shorts in the Harness
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| Illustration 2 | g00815132 |
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ECM connector P1 | |
- Disconnect the J1/P1 ECM connector and the J508/P508 fan control solenoid connector.
- Measure the resistance between P1:43 (Fan Control Solenoid) and chassis ground.
- Measure the resistance between P1:51 (Solenoid Return) and chassis ground.
- Measure the resistance between P1:43 (Fan Control Solenoid) and P1:51 (Solenoid Return).
Expected Result:
The resistance for each measurement should be greater than 20,000 Ohms.
Results:
- OK - Proceed to Test Step 5.
- Not OK - There is a short between the ECM and the fan control solenoid.
Repair: Repair the circuit.
STOP
Test Step 5. Check for Open Circuits in the Harness
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| Illustration 3 | g00815132 |
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ECM connector P1 | |
- Ensure that the keyswitch is in the OFF/RESET position and that the J1/P1 ECM connector is disconnected.
- Use a suitable piece of wire to short P1:43 (Fan Control Solenoid) and P1:51 (Solenoid Return).
- Disconnect the J508/P508 fan ontrol solenoid connector.
- Measure the resistance between P508:1 (Fan Control Solenoid) and P508:2 (Solenoid Return).
Expected Result:
The resistance should be less than 10 Ohms.
Results:
- OK - Proceed to Test Step 6.
- Not OK - There is an open circuit in the wiring harness between the fan control solenoid and the ECM.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP
Test Step 6. Measure the Current to the Fan Control Solenoid
- Reconnect the J1/P1 ECM connector.
- The J508/P508 fan control solenoid connector should still be disconnected. Install a jumper wire between J508:2 and P508:2.
- Connect an ammeter that is capable of withstanding a 5 Amp current between J508:1 and P508:1.
- Start the engine and observe the reading on the ammeter that is installed in the circuit.
- Turn the keyswitch to the OFF/RESET position.
- Remove the ammeter and the jumper wire from the circuit and reconnect the J508/P508 fan control solenoid connector.
Expected Result:
The ECM should be supplying between 0.3 and 1.6 Amp to the fan control solenoid.
Results:
- OK - The ECM appears to be supplying the correct current to the solenoid. Either the pump or the motor may not be responding correctly.
Repair: Troubleshoot the hydraulic system. Refer to Testing and Adjusting, "Hydraulic System"
.STOP
- Not OK - The ECM may not be producing a valid supply.
Repair: Verify your results.
Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.
Verify that the repair eliminates the problem.
STOP