Cooling Fan Inoperative (Single Fan)
Cooling Fan Inoperative (Single Fan)
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 engine cooling fan system consists of one electrical cooling fan, a serviceable resistor module mounted in the cooling fan shroud, and three fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate the fan at low, medium, or high speeds, depending on cooling requirements. The resistor module is a self-contained unit providing a specific resistance through three individual circuits. To activate the fan, the ECM applies ground to the coil side of the applicable fan relays. The cooling fan and fan relays receive battery voltage from the underhood fuse block. The ground path for the operation of the cooling fan is provided at G104.
Diagnostic Aids
* The scan tool cooling fan output control operates as follows:
- Cooling Fan Relay 1 operates the fan at a low speed
- Cooling Fan Relay 2 and 3 operates the fan at a medium speed
- Cooling Fan Relay 1, 2 and 3 operates the fan at a high speed
* KR20 cooling fan relay identification:
- KR20C cooling fan low speed FAN 1 Relay
- KR20D cooling fan high speed FAN 2 Relay
- KR20E cooling fan speed control FAN 3 or S/P Relay
* When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.
Reference Information
Schematic Reference
Engine Cooling Schematics (Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Cooling Fan Description and Operation (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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0480, P0481, P0691, P0692, P0693 or P0694 is not set.
• If a DTC is set, refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 (w/LLT) (P0480)DTC P0480, P0481, P0691, P0692, P0693, or P0694 (w/LLT and Dual Fan) (P0480).
2. Ignition ON, command the fan relays ON and OFF with a scan tool. Verify that the fan operates at low, medium and high speed.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the R10 cooling fan resistor.
2. Test for less than 5 ohm between the cooling fan motor ground circuit terminal 2 and ground.
• If greater than the specified range, test the ground circuit for and open/high resistance.
3. Connect a test lamp between the G10 cooling fan motor voltage supply circuit terminal 4 and ground. Command the FC relay 1 ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.
• If the test lamp remains OFF all of the time, test the voltage supply circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the KR20C relay.
4. Connect a test lamp between the G10 cooling fan motor voltage supply circuit terminal 3 and ground. Command the FC relay 2 and 3 ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.
• If the test lamp remains OFF all of the time, test the voltage supply circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the KR20D relay.
5. Connect a test lamp between the G10 cooling fan motor voltage supply circuit terminal 1 and ground. Command the FC relay 2 and 3 ON and OFF with a scan tool. The test lamp should remain OFF.
• If the test lamp illuminates, test or replace the KR20E relay.
6. Connect a test lamp between the G10 cooling fan motor voltage supply circuit terminal 1 and ground. Command the FC relay 1, 2 and 3 ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.
• If the test lamp remains OFF all of the time, test the voltage supply circuit for an open/high resistance or a short to ground. If the circuit tests normal, test or replace the KR20E relay.
7. Connect the harness connector at the R10 cooling fan resistor. Disconnect the harness connector at the G10 cooling fan motor.
8. Connect a test lamp between the voltage supply circuit terminal 1 and the ground circuit terminal 2. Command the cooling fans ON in all 3 speeds. Verify the test lamp illuminates in all 3 speeds.
• If the test does not illuminate in all 3 speeds, replace the R10 cooling fan resistor.
9. If all circuits/connections test normal, replace the G10 cooling fan motor.
Component Testing
1. Ignition OFF, disconnect the appropriate KR20 cooling fan relay.
2. Test for 200-240 ohm between terminals 85 and 86 of the relay.
• If not within the specified range, replace the KR20 cooling fan relay.
3. Test for infinite resistance between the terminals listed below.
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If not the specified value, replace the relay.
4. Test for less than 2 ohm between terminals 30 and 87A.
• If greater than the specified range, replace the KR20E cooling fan relay.
5. Install a 20 A fused jumper wire between B+ and relay terminal 85. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.
• If greater than the specified range, replace the KR20 cooling fan relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Engine Coolant Fan Motor Replacement (LF1, LLT) (Service and Repair)Engine Coolant Fan Motor Replacement (LSA) (Service and Repair)
* Engine Coolant Fan Resistor Replacement (LF1, LLT) (Service and Repair)