Cooling Fan Always On
Cooling Fan Always On (LEA)
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 is composed of one cooling fan, a series of 3 relays, the engine control module (ECM), and the associated wiring. The cooling fan motor assembly includes two resistors. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits. The underhood fuse block supplies the cooling fan relays with B+ at the switch side, and ignition voltage at the coil side of the relays through separate fuses. When the cooling fan is commanded ON, the ECM grounds the appropriate relay control circuit, which energizes the relay coil. The magnetic field, created within the relay by the energized relay coil, overcomes the spring tension of the bi-metal switch armature causing the relay switch to close. When the relay switch closes, B+ is supplied to the cooling fan motor through the relay controlled output circuit, causing the cooling fan motor to operate. A dedicated ground is supplied to the cooling motor to complete the circuit.
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
* Certain resistance conditions with IAT or ECT sensors may cause unwarranted cooling fan activation. If the ECM is commanding the cooling fan ON for no apparent reason and without any component or system DTCs set, the IAT or ECT sensor may be skewed. If this condition is suspected, refer to the Temperature Versus Resistance tables in the appropriate engine controls subsection.
* If the cooling fan operates at high speed when only low speed is commanded ON and the fan operates normally at medium speed, test or replace the KR20D Cooling Fan High Speed Relay.
Reference Information
Schematic Reference
Engine Heating/Cooling Schematics [1][2]Cooling System
Connector End View Reference
Component Connector End Views Outside Rearview Mirror - Driver
Description and Operation
Cooling Fan Description and Operation (LEA) Cooling Fan Description and OperationCooling Fan Description and Operation (LHU) Cooling Fan 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.
2. Verify that there are no cooling system DTCs set.
• If a DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
• If no DTC is not set
3. Verify the scan tool parameters listed below display OFF.
* Cooling Fan Relay 1 Command
* Cooling Fan Relays 2 and 3 Command
• If a scan tool parameter displays ON
Refer to Diagnostic Aids and Symptoms - Engine Cooling Symptoms - Engine Cooling for further diagnosis.
• If both scan tool parameters display OFF
4. Verify that the G10 Cooling Fan Motor is not operating.
• If the G10 Cooling Fan Motor is operating
Refer to Circuit/System Testing.
• If the G10 Cooling Fan Motor is OFF
5. All OK.
Circuit/System Testing
1. Ignition OFF, disconnect the KR20C Cooling Fan Low Speed Relay, ignition ON.
2. Verify that the G10 Cooling Fan Motor is OFF.
• If the G10 Cooling Fan Motor is OFF
Test or replace the KR20C Cooling Fan Low Speed Relay.
• If the G10 Cooling Fan Motor is ON
3. Ignition OFF, disconnect the KR20P Cooling Fan Medium Speed Relay, ignition ON.
4. Verify the G10 Cooling Fan Motor is OFF.
• If the G10 Cooling Fan Motor is ON
1. Ignition OFF, remove the KR20D Cooling Fan High Speed Relay and disconnect the harness connector at the G10 Cooling Fan Motor, ignition ON.
2. Test for less than 1 V between the terminals listed below and ground:
* KR20C Cooling Fan Low Speed Relay terminal 87
* KR20D Cooling Fan High Speed Relay terminal 87
* KR20P Cooling Fan Medium Speed Relay terminal 87
• If 1 V or greater, repair the short to voltage in the relay controlled output circuit.
• If the G10 Cooling Fan Motor is OFF
5. Test or replace the KR20P Cooling Fan Medium Speed Relay.
Component Testing
1. Ignition OFF.
2. Disconnect the appropriate cooling fan relay.
3. Test for 65-105 ohms between terminals 85 and 86.
• If less than 65 ohms or greater than 105 ohms
Replace the appropriate cooling fan relay.
• If between 65-105 ohms
4. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
OR
* 3 and 2
* 3 and 5
* 3 and 1
* 1 and 5
• If less than infinite resistance
Replace the appropriate cooling fan relay.
• If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85 and 12 V.
6. Install a jumper wire between relay terminal 86 and ground.
7. Test for less than 2 ohms between terminals 30 and 87.
• If 2 ohms or greater
Replace the appropriate cooling fan relay.
• If less than 2 ohms
8. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)