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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 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

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

* Electrical Center Identification Views Application and ID

Description and Operation

Cooling Fan Description and Operation Cooling Fan

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 a DTC is set
Refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 P0480.

• If no DTCs is set

3. Verify that both cooling fans turn ON and OFF and operate at low and high speed, when commanding the appropriate cooling fan relays ON and OFF with a scan tool.

• If a cooling fan does not operate
Refer to Circuit/System Testing

• If both cooling fans operate

4. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect all of the KR20 Cooling Fan Relays.

2. Verify a test lamp illuminates between ground and the B+ circuit terminals listed below:

* KR20C Cooling Fan Low Speed B+ circuit terminal 30/3

* KR20D Cooling Fan High Speed B+ circuit terminal 87/5

• If the test lamp does not illuminate and the circuit fuse is good

1. Disconnect the appropriate cooling fan fuse.

2. Test for less than 2 ohms between the fuse and the appropriate relay B+ circuit terminal, end to end.

• If 2 ohms or greater, repair the open/high resistance in the B+ circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Connect a DMM to the appropriate relay B+ circuit terminal.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the B+ circuit.

• If infinite resistance

3. Disconnect the harness connector at the appropriate G10 Cooling Fan Motor.

4. Test for infinite resistance between the appropriate relay controlled output circuit terminal 87/5 and ground.

* KR20C Cooling Fan Low Speed output circuit terminal 87/5

* KR20D Cooling Fan High Speed output circuit terminal 30/3

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, test or replace the appropriate G10 Cooling Fan Motor.

• If the test lamp illuminates

3. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the G10L Cooling Fan Motor-Left. It may take up to 2 minutes for all vehicle systems to power down.

4. Test for less than 5 ohms between the circuits listed below and ground:

* G10L Cooling Fan Motor-Left terminal A

* KR20E Cooling Fan Speed Control Relay terminal 87/5

• If 5 ohms or greater

1. Ignition OFF and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 2 ohms in the appropriate ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 5 ohms

5. Connect the harness connector at the G10L Cooling Fan Motor-Left.

6. Connect a 50 A fused jumper between the KR20D Cooling Fan High Speed Relay terminals 30/3 and 87/5.

7. Verify the G10L Cooling Fan Motor-Left is activated at high speed.

• If the cooling fan does not activate

1. Disconnect the harness connector at the G10L Cooling Fan Motor-Left.

2. Test for less than 2 ohms in the circuit between KR20D Cooling Fan High Speed Relay terminal 30/3 and the G10L Cooling Fan Motor-Left terminal B.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the G10L Cooling Fan Motor-Left.

• If the cooling fan activates

8. Connect a fused jumper between the KR20E Cooling Fan Speed Control Relay switch circuit terminal 30/3 and the ground circuit terminal 87/5.

9. Connect a 40 A fused jumper between the KR20C Cooling Fan Low Speed Relay terminals 30/3 and 87/5.

10. Verify the G10R Cooling Fan Motor-Right is activated at high speed.

• If the cooling fan does not activate

1. Disconnect the harness connector at the G10R Cooling Fan Motor-Right.

2. Test for less than 2 ohms in the circuit between KR20C Cooling Fan Low Speed Relay terminal 87/5 and the G10R Cooling Fan Motor-Right terminal B.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms

3. Test for less than 2 ohms in the circuit between KR20E Cooling Fan Speed Control Relay terminal 30/3 and the G10R Cooling Fan Motor-Right terminal A.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the G10R Cooling Fan Motor-Right.

• If the cooling fan activates

11. Install the KR20E Cooling Fan Speed Control Relay.

12. Verify both fan motors activate at low speed.

• If both cooling fans do not activate at low speed

1. Disconnect both cooling fan motor harness connectors and the KR20E Cooling Fan Speed Control Relay.

2. Test for less than 2 ohms in circuit between KR20E Cooling Fan Speed Control Relay terminal 87A/4 and the G10L Cooling Fan Motor-Left terminal B.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms

3. Test for infinite resistance between KR20E Cooling Fan Speed Control Relay terminal listed below and ground.

* KR20E Cooling Fan Speed Control Relay terminal 30/3

* KR20E Cooling Fan Speed Control Relay terminal 87A/4

• If less than infinite, repair the short to ground in the circuit.

• If infinite, replace the KR20E cooling fan speed control relay.

• If both cooling fans activate

13. Test or replace the cooling fan relay listed below as appropriate:

* KR20C Cooling Fan Low Speed Relay

* KR20D Cooling Fan High Speed Relay

Component Testing

1. Ignition OFF.

2. Disconnect a 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 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
OR

* 3 and 2

* 3 and 5

* 3 and 1

* 1 and 5

• If less than infinite resistance
Replace the KR20 Cooling Fan Relay.

• If infinite resistance

Note: This test only applies to the speed control relay.

5. Test for less than 2 ohms between KR20E Cooling Fan Speed Control Relay terminals 30/3 and 87A/4.

• If 2 ohms or greater
Replace the KR20E Cooling Fan Speed Control Relay.

• If less than 2 ohms

6. Install a 20 A fused jumper wire between relay terminal 85 or 2 and 12 V.

7. Install a jumper wire between relay terminal 86 or 1 and ground.

8. Test for less than 2 ohms between terminals 3/30 and 87/5.

• If 2 ohms or greater
Replace the KR20 Cooling Fan Relay.

• If less than 2 ohms

9. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)

* Engine Coolant Fan Replacement Service and Repair

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