Cooling Fan Always On
Cooling Fan Always On (LUW, LWE)
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 provide an overview of each diagnostic category.
Circuit/System Description
The engine cooling fan system consists of a cooling fan assembly containing one electric cooling fan. The engine control module (ECM) uses two fan control circuits and a series of two relays to command the fans ON in either high speed or low speed, depending on cooling requirements. The ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. Each driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. In low speed, the fan is turned ON at a reduced speed. High speed has the fan turned ON at full speed.
Diagnostic Aids
* The scan tool cooling fan output control operates as follows:
- Cooling Fan Relay 1 operates both fans at a low speed
- Cooling Fan Relay 2 operates one 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 fans 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.
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 Fan Description and Operation (LUV) Cooling Fan Description and OperationCooling Fan Description and Operation (LWE, LUW) 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 DTC P0480, P0481, P0691, P0692, P0693, or P0694 is not set.
• If any of the DTCs are set
Refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 (LUW, LWE) P0480.
• If none of the DTCs are set
3. Verify the scan tool parameters listed below display OFF:
* Cooling Fan Relay 1 Command
* Cooling Fan Relays 2 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 fan is not activated.
• If a fan is operating
Refer to Circuit/System Testing.
• If the fan is OFF
5. All OK.
Circuit/System Testing
Cooling Fan Always ON
1. Ignition OFF, disconnect KR20C Cooling Fan Low Speed Relay and KR20D Cooling Fan High Speed Relay, ignition ON.
2. Verify that the cooling fan is OFF.
• If the cooling fan is ON
1. Ignition OFF, disconnect the harness connector at the G10R Cooling Fan Motor, ignition ON.
2. Test for less than 1 V between the appropriate output control circuit terminal 87 and ground.
• If 1 V or greater, repair the short to voltage in the circuit.
• If the cooling fan is OFF
3. Test or replace the appropriate cooling fan relay.
Component Testing
1. Ignition OFF.
2. Disconnect the KR20 Cooling Fan Relay.
3. Test for 70-110 ohms between terminals 85/2 and 86/1.
• If less than 70 ohms or greater than 110 ohms
Replace the appropriate
KR20 cooling fan relay.
• If between 70-110 ohms
4. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than infinite resistance
Replace the appropriate KR20 Cooling Fan Relay.
• If infinite resistance
5. Install a 20 A fused jumper wire between relay terminal 85 or 2 and 12 V.
6. Install a jumper wire between relay terminal 86 or 1 and ground.
7. Test for less than 2 ohms between terminals 3/30 and 5/87.
• If 2 ohms or greater
Replace appropriate the KR20 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)