The cooling fan relay sends a pulse width modulation (PWM) signal of 12-14 volts to the cooling fan clutch through the cooling fan clutch supply voltage circuit. The control module uses this PWM signal in order to control the speed of the cooling fan clutch. The signal controls the position of the oil control valve inside the cooling fan clutch. If the cooling fan RPM is different than the control module is expecting, DTC P0483 will set. The actual cooling fan RPM vs the desired cooling fan RPM is not always exactly the same. There can be up to an 800 RPM difference. If the control module detects that the cooling fan speed is over 6,800 RPM then DTC P0493 will set.

P0483

P0493

The engine is running.

P0483

The difference between commanded and actual cooling fan speed is greater than 1,000 RPM for 100 seconds.

P0493

The cooling fan RPM is greater than 6,800 RPM.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. Ignition OFF, inspect the cooling fan and the drive belt for the following conditions:

•	A cracked drive belt

•	A loose or a worn drive belt

•	A misrouted drive belt

•	Oil leaks at the cooling fan clutch

•	A free-spinning cooling fan

•	A seized cooling fan clutch

•	A broken cooling fan

2. Idle the engine.
3. Command the cooling fan clutch to 10 percent.
4. Operate the engine at 2,000 RPM for 2 minutes. The fan should be quiet to indicate the clutch is disengaged.
5. Command the cooling fan clutch to 80 percent.
6. Operate the engine at 2,000 RPM for 2 minutes. The fan should be loud to indicate the clutch is engaged.
7. Operate the vehicle within the Conditions for Running and Setting the DTC, and verify the DTC does not set.

⇒	If the DTC sets, proceed with Circuit/System Testing.

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the fan relay.
2. Measure between the fan relay ground circuit terminal 6 and ground for less than 3 ohms.

⇒	If more than the specified range, test the ground circuit for an open/high resistance.

3. Operate the engine at 2,000 RPM for 2 minutes. The fan should be quiet to indicated the clutch is disengaged.

⇒	If not disengaged, test the cooling fan clutch supply voltage circuit for a short to voltage. If the circuit tests normal, replace the clutch.

4. Ignition OFF, install a 10A fused jumper wire between the positive terminal at the battery and the cooling fan clutch supply voltage circuit terminal 4.
5. Operate the engine at 2,000 RPM for 2 minutes. The fan should be loud to indicated the clutch is engaged.

⇒	If not engaged, test the cooling fan clutch supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the fan clutch ground circuit for an open/high resistance. If the circuits test normal, replace the clutch.

6. Ignition OFF, install a 10A fused jumper wire between the relay voltage supply circuit terminal 2 and the cooling fan clutch supply voltage circuit terminal 4.
7. Operate the engine at 2,000 RPM for 2 minutes. The fan should be loud to indicated the clutch is engaged.

⇒	If not engaged, test the relay voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.

8. Connect a test lamp between the positive terminal at the battery and the cooling fan clutch relay control circuit terminal 5.
9. Engine RUNNING at 2,000 RPM, command the cooling fan clutch to 70 percent for 2 minutes. The test lamp should turn on steady or flash, indicating that the control module can control the relay.

⇒	If the lamp does not flash or turn on steady, test the cooling fan clutch control circuit for a short to ground, a short to voltage, or an open/high resistance. If the circuit tests normal, replace the control module.

10. Perform the relay component test. The relay should test normal.

⇒	If the relay does not test normal, replace the relay.

11. Ignition OFF, disconnect the fan clutch at the shroud.
12. Measure between the low reference circuit terminal C and ground for less than 3 ohms.

⇒	If more than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the control module.

13. Ignition ON, measure between the 5-volt reference circuit terminal E and the low reference circuit terminal C for 4.8-5.2 volts.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.

⇒	If more than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the control module.

14. Install jumper wires in the 5-volt reference and low reference circuits between the harness and pigtail connectors at the shroud.

•	5-volt reference circuit--terminals E

•	Low reference circuit--terminals C

15. Measure DC voltage between the signal circuit terminal D at the sensor pigtail connector and the 5-volt reference circuit jumper wire terminal.
16. Ignition ON, rotate the fan by hand. The voltage should toggle between approximately 5 volts and 0 volts.

⇒	If the voltage does not toggle correctly, test the 3 circuits in the pigtail harness for a short to ground, a short to voltage, or an open/high resistance. If the circuits test normal, replace the clutch.

17. Leave the jumpers from the previous step in place. Measure voltage between the signal circuit terminals D of the harness and pigtail connectors at the shroud.
18. Rotate the fan by hand. The voltage should toggle between approximately 5 volts and 0 volts.

⇒	If the voltage does not toggle correctly, test the signal circuit for a short to ground, a short to voltage, or an open/high resistance. If the circuit tests normal, replace the control module.

19. If all circuits, the relay, and the speed sensor test normal, replace the clutch.

Relay Test

1. Connect the relay ground terminal to ground and the voltage supply terminal to appropriately fused power to energize the relay.
2. Test for less than 1 volt between the load voltage supply terminal and ground.
3. Connect the relay control circuit terminal to ground.
4. Test for B+ between the load voltage supply terminal and ground.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.