Cooling Fan Inoperative (LUV)
Cooling Fan Inoperative (LUV)
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.
Diagnostic Fault Information
Circuit/System Description
The engine cooling fan system is composed of one fan, 3 relays, the engine control module (ECM), and the associated wiring. The fan assembly includes two resistors, which enable the fan to operate at 3 speeds.
Low Speed
In low speed operation, the ECM provides ground from ECM terminal 41 X1. The Cooling Fan Speed Control Relay activates and provides power to the cooling fan motor through cooling fan resistor terminal 2.
Medium Speed
In medium speed operation, the ECM provides ground from ECM terminal 54 X1. The Cooling Fan Medium Speed Relay activates and provides power to the cooling fan motor through cooling fan resistor terminal 3.
High Speed
In high speed operation, the ECM provides ground from ECM terminal 41 X1 and 54 X1. As previously described, power is now provided to both cooling fan terminals 2 and 3. In addition, power and ground are now provided to the coil of the Cooling Fan High Speed Relay. The Cooling Fan High Speed Relay activates and provides power to the cooling fan motor, bypassing the cooling fan resistor.
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Cooling System 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 Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, verify that DTCs P0480 or P0481 are not set.
2. Command the Cooling fan relay 1 ON and OFF with a scan tool. The cooling fan should operate on low speed when commanded ON, and turn OFF when commanded OFF.
• If not the specified value, refer to Circuit/System Testing.
3. Command the Cooling fan relay 2 ON and OFF with a scan tool. The cooling fan should operate on medium speed when commanded ON, and turn OFF when commanded OFF.
• If not the specified value, refer to Circuit/System Testing.
Circuit/System Testing
Note:
You must perform the circuit/system verification before proceeding with circuit/system testing.
1. Ignition OFF, disconnect the relays listed below:
* KR20E Cooling Fan Speed Control Relay
* KR20D Cooling Fan High Speed Relay
* KR20P Cooling Fan Medium Speed Relay
2. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground:
* KR20E Cooling Fan Speed Control Relay terminal 30
* KR20D Cooling Fan High Speed Relay terminal 30
* KR20P Cooling Fan Medium Speed Relay terminal 30
• If the test lamp does not illuminate, test the B+ circuits for a short to ground or an open/high resistance.
3. Verify that a test lamp illuminates between the ignition circuit terminals listed below and ground:
* KR20E Cooling Fan Speed Control Relay terminal 86
* KR20D Cooling Fan High Speed Relay terminal 86
* KR20P Cooling Fan Medium Speed Relay terminal 86
• If the test lamp does not illuminate, test the ignition circuits for a short to ground or an open/high resistance.
4. Disconnect the harness connector at the G10 Cooling Fan Motor.
5. Test for less than 5 ohms between ground circuit terminal 1 and ground.
• If greater than 5 ohms, test the ground circuit for an open/high resistance.
6. Connect the harness connector at the G10 Cooling Fan Motor.
7. Install a 50 A fused jumper wire between the control circuit terminal 87 at the KR20D Cooling Fan High Speed Relay and B+.
8. Verify that the cooling fan is operating.
• If the cooling fan is not operating, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the G10 Cooling Fan Motor.
9. Reconnect all fan relays.
10. Command the Cooling Fan Relay 1 ON with a scan tool. The cooling fan should operate on low speed.
• If the cooling fan is not operating, test or replace the KR20E Cooling Fan Speed Control Relay and verify the cooling fan operates. If the cooling is not operating, replace the K20 Engine Control Module.
11. Test for greater than 11 V between the control circuit terminal 86 at the KR20D Cooling Fan High Speed Relay and ground while commanding ON the Cooling Fan Relay 1 with a scan tool.
• If less than 11 V, test the control circuit for an open/high resistance. If the circuit tests normal, replace the KR20E Cooling Fan Speed Control Relay.
12. Command the Cooling Fan Relay 2 ON with a scan tool. The cooling fan should operate on medium speed.
• If the cooling fan is not operating, test or replace the KR20P Cooling Fan Medium Speed Relay and verify the cooling fan operates. If the cooling is not operating, replace the K20 Engine Control Module.
13. Connect a test lamp between the control circuit terminal 85 at the KR20D Cooling Fan High Speed Relay and B+.
14. Verify the test lamp illuminates while commanding ON the Cooling Fan Relay 2 with a scan tool.
• If the test lamp does illuminate, test the control circuit for an open/high resistance.
15. If the circuits test normal, replace the KR20D Cooling Fan High Speed Relay.
Component Testing
Relay Test
1. Ignition OFF, disconnect the applicable relay.
2. Test for 70-110 ohms between terminal 85 and 86 of the relay.
• If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* Terminals 30 and 86
* Terminals 30 and 87
* Terminals 30 and 85
* Terminals 85 and 87
* Terminals 86 and 87
• If not the specified value, replace the relay.
4. Install a 20 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
• If greater than the specified value, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for Engine Control Module replacement, programming and setup