Cooling Fan Inoperative
Cooling Fan Inoperative (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, inspect the cooling fan and the drive belt for the following conditions:
* 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 X142 and the fan clutch jumper harness for the following conditions:
- 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
2. Ignition ON, observe the DTC information with a scan tool. 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
Note: In each of the commanded states, it may take up to 2 minutes for the Fan Speed to achieve the Desired Fan Speed.
3. Engine at operating temperature, operate the engine at 1,500 RPM while slowly commanding the cooling fan clutch from 10 % to 80 %, then return to 10 %. Observe the difference between the scan tool Fan Speed and Desired Fan Speed parameters throughout the test. The difference between the parameters should be less than 500 RPM throughout the speed transition.
• The fan clutch does not operate as specified
Refer to Circuit/System Testing
• The fan clutch operates as specified
4. All OK
Circuit/System Testing
1. Ignition OFF, disconnect the fan clutch harness connector X142.
2. Test for less than 5 ohms between the fan clutch solenoid valve ground circuit terminal A and ground.
• If 5 ohms or greater
Test the ground circuit for an open/high resistance.
• If less than 5 ohms
3. Connect a test lamp between the cooling fan clutch solenoid voltage control circuit terminal B and ground.
Note: Ensure that the test lamp and harness connector are positioned away from the cooling fan, drive belt, and pulleys.
4. Engine operating, command the fan clutch relay to 50 % with a scan tool. The test lamp should illuminate and flash ON and OFF.
• If the test lamp does not illuminate
1. Ignition OFF, disconnect the cooling fan clutch relay.
2. Test for less than 5 ohms between the fan relay ground circuit terminal 6 and ground.
• If 5 ohms or greater
Test the ground circuit for an open/high resistance.
• If less than 5 ohms
3. Test for less than 1 ohms between the relay B+ circuit terminal 2 and the Fan Fuse.
• If 1 ohms or greater
Test the B+ circuit for an open/high resistance.
• If less than 1 ohms
4. Test for infinite resistance between the fan clutch relay terminal 4 and ground.
• If less than infinite
Test the fan clutch solenoid valve voltage control circuit for a short to ground.
• If infinite
5. Test for less than 1 ohms between relay terminal 4 and harness connector X142.
• If 1 ohms or greater
Test the fan clutch solenoid valve voltage control circuit for an open/high resistance.
• If less than 1 ohms
Test or replace the fan clutch relay.
• If the test lamp illuminates and flashes
Note: Perform the following steps at the fan side of the fan clutch jumper harness. Ensure that the jumper harness is connected to the fan clutch.
5. Test for infinite resistance between the terminals of the fan clutch harness connector listed below.
* B and C
* B and D
* B and E
* B and the fan clutch housing
• If less than the specified range
Test the circuits of the jumper harness for an open/shorted condition. If the jumper harness tests normal, replace the cooling fan clutch assembly.
• If at the specified range
6. Test for 7-17 ohms between terminal B and terminal A of the fan clutch jumper harness connector.
• If not within the specified range
Test the circuits of the jumper harness for an open/shorted condition. If the jumper harness tests normal, replace the cooling fan clutch assembly.
• If within the specified range
Refer to EV Fan Clutch Solenoid Valve Test-Dynamic
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.
EV Fan Clutch Solenoid Valve Test-Dynamic
1. Ignition OFF, disconnect the fan clutch jumper harness connector X142.
2. Connect a jumper wire between terminal A of the jumper harness connector and ground.
3. Connect a 10 A fused jumper wire to terminal B of the jumper harness connector.
Note:
* Ensure that the jumper wires and harness connector are positioned away from the cooling fan, drive belt, and pulleys.
* It may take several minutes for the fan clutch to fully engage with the engine at idle.
4. Connect the 10 A fused jumper wire to B+. The fan should get much louder to indicate the 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
5. 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.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Fan Clutch Replacement (Diesel) Service and Repair