Cooling Fan Always On (LFW)
Cooling Fan Always On (LFW)
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 a cooling fan assembly containing two electric cooling fans. The engine control module (ECM) uses two fan control circuits and a series of three 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, both fans are turned ON at a reduced speed. High speed has both fans 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 Relays 2 and 3 operates one fan at a high speed
- Cooling Fan Relays 1, 2 and 3 operates both fans 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 appropriate temperature versus resistance table listed below:
V6
* Temperature Versus Resistance - Engine Coolant Temperature Sensor
* Temperature Versus Resistance - Intake Air Temperature Sensor (Hitatchi Sensor) Temperature Versus Resistance - Intake Air Temperature Sensor (Hitatchi Sensor)
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
* Component Connector End Views Sunshade - Left (DH6)
* Electrical Center Identification Views X70A Relay Block - Underhood Top View
Description and Operation
Cooling Fan Description and Operation (LFW) Cooling Fan Description and Operation (LFW)Cooling Fan Description and Operation (LBN, LEA, LE9, LLU, or LTD) Cooling Fan Description and Operation (LBN, LEA, LE9, LLU, or LTD)
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. Engine operating, observe the DTC information with a scan tool. DTC P0480 P0481, P0691, P0692 , P0693, or P0694 should not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Ignition ON, observe the scan tool parameters listed below:
* Cooling Fan Relay 1 Command
* Cooling Fan Relays 2 and 3 Command
The parameters should display OFF.
3. Ignition ON, observe that the fans are not activated.
Circuit/System Testing
1. Ignition OFF, disconnect KR20C cooling fan relay.
2. Ignition ON, observe that the cooling fans are not activated.
• If both fans remain ON, test the KR20C relay controlled output circuit for a short to voltage.
• If both the fans are OFF, test or replace the KR20C low speed cooling fan relay.
3. Ignition OFF, disconnect the KR20D relay.
4. Ignition ON, observe that the left cooling fan is OFF.
• If the fan remains ON, test the relay controlled output circuit for a short to voltage.
5. If the circuit tests normal, test or replace the KR20D relay.
Component Testing
KR20 Relay with Double Digit Terminal ID
1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohms between terminals 85 and 86.
• If not within the specified range, replace the KR20 cooling fan relay.
3. Measure the resistance between the terminals listed below. The DMM should display OL.
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than the specified range, replace the KR20 cooling fan relay.
Note:
The following test applies to the KR20E relay only.
4. Test for less than 2 ohms between terminals 30 and 87A.
• If greater than the specified range, replace the KR20E relay.
5. Connect a 20 A fused jumper wire between relay terminal 85 and B+. Connect 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 range, replace the KR20 cooling fan relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)