Fan Clutch: Testing and Inspection
Fan Clutch Diagnosis (Diesel)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The ECM controls the EV fan clutch operation. The ECM regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the ECM command increases, so does the ON time of the relay. The relay ON time directly controls the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, which increases the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and allows the fluid in the coupling of the fan clutch to drain back to the storage chamber, which reduces fan speed. The rapid modulation of the fan clutch solenoid valve gives the ECM the ability to precisely control the amount of fluid that remains in the fluid coupler, allowing more effective regulation of the fan speed and powertrain cooling requirements.
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
* Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
* Electrical Center Identification Views Fuse Block - Underhood Label
Description and Operation
Cooling Fan Description and Operation (Gas) Description and OperationCooling Fan Description and Operation (Diesel) Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition OFF.
2. Verify the conditions listed below do not exist with the cooling fan system:
* A loose, worn, or mis-routed drive belt
* Oil leaks at the cooling fan clutch
* A free-spinning cooling fan
* A seized cooling fan clutch
* A broken cooling fan
* Inspect the cooling fan clutch harness connector and the fan clutch jumper harness for the conditions listed below:
- Poorly mated connectors
- Backed/pushed out connector terminals
- Poor terminal tension
- Cut, chaffed, or nicked harness wiring at the fan clutch
• If a condition is found
Repair as necessary
• If a condition is not found
3. Ignition ON.
4. Verify DTC P0480, P0483, P0495, or P0526 is not set.
• If a DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle
• If a DTC is not set
5. Engine at operating temperature.
6. Verify the scan tool Fan Speed and Desired Fan Speed parameters are within 500 RPM while performing the test listed below:
1. Increase engine speed to 1,500 RPM
Note: In each of the commanded states, it may take up to 2 minutes for the Fan Speed to achieve the Desired Fan Speed.
2. Command the Cooling Fan slowly from 10 % to 80 % with a scan tool.
3. Command the Cooling Fan to 10 % with a scan tool.
• The Fan Speed is not within 500 RPM of the Desired Fan Speed
Refer to Circuit/System Testing
• The Fan Speed is within 500 RPM of the Desired Fan Speed
7. All OK
Circuit/System Testing
1. Ignition OFF, and all vehicle systems OFF, disconnect the cooling fan relay. It may take up to 2 minutes for all vehicle systems to power down.
2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground.
• If the test lamp does not illuminate
1. Remove the Fan Fuse.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is OK and there is voltage at the fuse.
• If the test lamp illuminates
3. Test for less than 5 ohms between the fan relay ground circuit terminal 6 and ground.
• If 5 ohms or greater
1. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
4. Test for 7-17 ohms between fan relay terminal 4 and terminal 6.
• If less than 7 ohms
1. Disconnect the engine cooling fan harness connector.
2. Verify a test lamp does not illuminate between the fan relay terminal 4 and B+.
• If the test lamp illuminates, repair the short to ground in the solenoid valve control circuit terminal 4.
• If the test lamp does not illuminate, test the circuits of the jumper harness for a shorted condition. If the jumper harness tests normal, replace the cooling fan clutch assembly.
• If greater than 17 ohms
1. Disconnect the engine cooling fan harness connector.
2. Test for less than 2 ohms between relay terminal 4 and fan harness connector terminal B.
• If 2 ohms or greater, repair the open/high resistance in the fan clutch solenoid valve control circuit.
• If less than 2 ohms.
3. Test for less than 2 ohms between the fan harness connector terminal A and ground.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, test the circuits of the jumper harness for an open/high resistance condition. If the jumper harness tests normal, replace the cooling fan clutch assembly.
• If within 7-17 ohms
5. Engine operating, connect a 10 A fused jumper wire between fan relay terminal 4 and B+.
Note: It may take several minutes for the fan clutch to fully engage with the engine at idle.
6. Verify the fan gets much louder to indicate the fan clutch is engaged.
Note: It may take anywhere from 10-52 minutes for the fan clutch to disengage depending on the factors below:
* Engine speed
* Coupler fluid temperature
* Elevation above sea level
7. Disconnect the 10 A fused jumper wire from B+. The fan should become quiet to indicate the clutch is disengaged.
• If the fan clutch doesn't engage or disengage according to the test
Replace the cooling fan clutch assembly.
• If the fan clutch engages and disengages according to the test
8. Test or replace the fan relay.
Component Testing
Relay Test
1. Remove the cooling fan clutch relay.
2. Connect a 10 A fused jumper wire between relay terminal 2 and B+. Connect a jumper wire between relay terminal 6 and ground.
3. Test for less than 1 V between terminal 4 and ground.
• If greater than the specified value, replace the fan relay.
4. Connect a jumper wire between terminal 5 and ground.
5. Test for B+ between terminal 4 and ground.
• If less than the specified value, replace the fan relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Fan Clutch Replacement (Diesel) Service and Repair