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Cooling Fan Inoperative




Cooling Fan Inoperative

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 ECM has the capability of providing command to the fan relays even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM.

* 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

* 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 [1][2]Cooling System

Connector End View Reference

* Component Connector End Views Outside Rearview Mirror - Driver

* Electrical Center Identification Views X50A Fuse Block - Underhood Label

Description and Operation

Cooling Fan Description and Operation (Single Fan, 3 Speed) Cooling Fan Description and Operation (Single Fan, 3 Speed)

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Engine Control Module Scan Tool Information (LEA) Scan Tool Testing and Procedures for scan tool information

Circuit/System Verification

1. Verify that DTC P0480, P0481, P0691, P0692, P0693, or P0694 is not set.

• If a DTC is set, refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 P0480.

2. Ignition ON, command the appropriate fan relay ON and OFF with a scan tool. Verify that the fan operates at the appropriate speed in each of the commanded states.

Circuit/System Testing

Inoperative in All Speeds

1. Ignition OFF, disconnect the G10 cooling fan motor connector.

2. Test for less than 1 ohms between G10 terminal 1 and ground.

• If 1 ohms or greater, test the ground circuit for an open/high resistance.

3. If the circuit/connections tests normal, test or replace the G10 cooling fan motor.

Low/High Speed Inoperative

1. Ignition OFF, disconnect all of the KR20 cooling fan relays.

2. Ignition ON, verify that a test lamp illuminates between KR20C relay terminal 30 and ground.

• If the test lamp does not illuminate, test the KR20C relay B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuits listed below for a short to ground:

* KR20C terminal 87 to KR20D terminal 30

* KR20D terminal 87 to G10 terminal 4

If the circuits test normal, test or replace the G10 cooling fan motor.

3. Ignition OFF, connect the KR20C relay.

4. Disconnect the G10 cooling fan connector.

5. Connect a test lamp between KR20D relay terminal 30 and ground.

6. Ignition ON, command the cooling fan ON at low speed with a scan tool. Verify the test lamp illuminates.

• If the test lamp does not illuminate, test the KR20D relay switch B+ circuit terminal 30 for an open/high resistance. If the circuit tests normal, replace the KR20C low speed relay.

7. Connect a test lamp between G10 terminal 2 and ground.

8. Command the cooling fan ON at low speed with a scan tool. Verify the test lamp illuminates.

• If the test lamp does not illuminate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal and the B+ fuse is open, test the relay controlled output circuit for a short to ground. If the circuits test normal, replace the G10 cooling fan motor.

9. Ignition OFF, Install the KR20D relay.

10. Connect a test lamp between G10 terminal 4 and ground.

11. Ignition ON, command the cooling fan ON at high speed with a scan tool. Verify the test lamp illuminates.

• If the test lamp does not illuminate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, replace the KR20D high speed relay.

12. If all the circuits and relays test normal, test or replace the G10 cooling fan motor.

Medium Speed Inoperative

1. Ignition OFF, disconnect the KR20P medium speed relay.

2. Ignition ON, verify that a test lamp illuminates between KR20P relay terminal 30 and ground.

• If the test lamp does not illuminate, test the KR20P relay B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the G10 cooling fan motor.

3. Ignition OFF, connect the KR20P relay. Disconnect the G10 cooling fan connector.

4. Connect a test lamp between G10 terminal 3 and ground.

5. Ignition ON, command the cooling fan ON at medium speed with a scan tool. Verify the test lamp illuminates.

• If the test lamp does not illuminate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, replace the KR20P medium speed relay.

6. If all the circuits and relay test normal, test or replace the G10 cooling fan motor.

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.

4. 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)

* Engine Coolant Fan Replacement Service and Repair

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