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Cooling Fan Always On




Cooling Fan Always On (LAF, LEA, LUK)

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. 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

* 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 Engine Cooling Schematics

Connector End View Reference

* Component Connector End Views Connector End Views By Name

* Electrical Center Identification Views Application and ID

Description and Operation

Cooling Fan Description and Operation (LAF , LEA, LUK) Cooling Fan Description and OperationCooling Fan Description and Operation (LDK or 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 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 Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON, observe the scan tool Cooling Fan Relay 1 and Cooling Fan Relays 2 and 3 Command parameters. The parameters should display OFF.

3. Ignition ON, observe that the fan is 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 fans are OFF, test or replace the KR20C cooling fan low speed relay.

3. Ignition OFF, disconnect the KR20J cooling fan-left high speed 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 all of the circuits test normal, test or replace the KR20J 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 KR20K relay only.

4. Test for less than 2 ohms between terminals 30 and 87A.

• If greater than the specified range, replace the KR20K 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.

KR20 Relay with Single Digit Terminal ID

1. Ignition OFF, disconnect the KR20 cooling fan relay.

2. Test for 70-110 ohms between terminals 1 and 2.

• 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.

* 3 and 1

* 3 and 5

* 3 and 2

* 2 and 5

• If less than the specified range, replace the KR20 cooling fan relay.

Note:
The following test applies to the KR20K relay only.

4. Test for less than 2 ohms between terminals 3 and 4.

• If greater than the specified range, replace the KR20K relay.

5. Connect a 20 A fused jumper wire between relay terminal 2 and B+. Connect a jumper wire between relay terminal 1 and ground. Test for less than 2 ohms between terminals 3 and 5.

• 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)

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