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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 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two resistors. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.

Diagnostic Aids

* 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 Sunshade - Left (D61)

* Electrical Center Identification Views X50A Fuse Block - Underhood Label

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 DTC is set

3. Verify that the cooling fan operates at low, medium, and high speed, when commanding the appropriate cooling fan relays ON and OFF with a scan tool.

• If the cooling fan does not operate at all speeds
Refer to Circuit/System Testing.

• If the cooling fan operates at all speeds

4. All OK.

Circuit/System Testing

Inoperative in All Speeds

1. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.

2. Verify a test lamp illuminates between the ground circuit terminal 1 and B+

• If the test lamp does not illuminate

1. Ignition OFF, remove the test lamp.

2. Test for less than 2 ohms in the 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 the test lamp illuminates

3. Test or replace the G10 Cooling Fan Motor. Replace the cooling fan fuses if necessary.

Low, Medium or High Speed Inoperative

1. Disconnect the following cooling fan relays, ignition ON:

* KR20C Cooling Fan Low Speed Relay

* KR20D Cooling Fan High Speed Relay

* KR20E Cooling Fan Speed Control Relay

* KR20F Cooling Fan Relay

* KR20P Cooling Fan Medium Speed Relay

2. Verify a test lamp illuminates between ground and each of the cooling fan relay B+ circuit terminals listed below:

* KR20C Cooling Fan Low Speed Relay terminal 30

* KR20D Cooling Fan High Speed Relay terminal 5

* KR20P Cooling Fan Medium Speed Relay terminal 3

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

1. Ignition OFF, remove the test lamp.

2. Test for less than 2 ohms in the appropriate relay B+ circuit, end to end.

• If 2 ohms or greater, repair the open/high resistance in the 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. Ignition OFF, disconnect the harness connector at the G10 Cooling Fan Motor.

2. Test for infinite resistance between the appropriate relay controlled output circuit terminal listed below and ground:

* KR20C Cooling Fan Low Speed Relay terminal 87

* KR20D Cooling Fan High Speed Relay terminal 3

* KR20P Cooling Fan Medium Speed Relay terminal 5

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

• If infinite resistance, test or replace the G10 Cooling Fan Motor, replace the fuse as necessary.

• If the test lamp illuminates

3. Verify a test lamp illuminates between the KR20F Cooling Fan Relay output circuit terminal 87 and B+.

• If the test lamp does not illuminate

1. Ignition OFF, remove the test lamp.

2. Test for less than 2 ohms in the 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 the test lamp illuminates

4. Ignition OFF, Install the KR20F Cooling Fan Relay, ignition ON.

5. Verify a test lamp illuminates between ground and each of the cooling fan relay terminals listed below:

* KR20C Cooling Fan Low Speed Relay terminal 85

* KR20E Cooling Fan Speed Control Relay terminal 86 and 30

• If the test lamp does not illuminate at each terminal

1. Ignition OFF, remove the test lamp.

2. Test for less than 2 ohms in the appropriate relay ignition circuit, end to end.

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

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

• If the test lamp illuminates at each terminal

6. Command the cooling fan ON at low speed with a scan tool.

7. Verify a test lamp illuminates between B+ and each of the KR20 Cooling Fan Relay terminals listed below:

* KR20C Cooling Fan Low Speed Relay terminal 86

* KR20E Cooling Fan Speed Control Relay terminal 85

• If the test lamp does not illuminate

1. Ignition OFF, remove the test lamp and disconnect the KR20F Cooling Fan Relay.

2. Test for less than 2 ohms between the KR20F Cooling Fan Relay terminal 30 and the relay control circuit terminals listed below:

* KR20C Cooling Fan Low Speed Relay terminal 86

* KR20E Cooling Fan Speed Control Relay terminal 85

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

• If less than 2 ohms, replace the KR20F Cooling Fan Relay.

• If the test lamp illuminates

8. Ignition OFF, install the KR20E Cooling Fan Speed Control Relay, Ignition ON.

9. Command the cooling fan ON at low speed with a scan tool.

10. Verify a test lamp illuminates between ground and the KR20D High Speed Relay ignition circuit terminal 1.

• If the test lamp does not illuminate

1. Ignition OFF, remove the test lamp and disconnect the KR20E Cooling Fan Speed Control Relay.

2. Test for less than 2 ohms between the KR20D High Speed Relay terminal 1 and KR20E Cooling Fan Speed Control Relay 87

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

• If less than 2 ohms, replace the KR20E Cooling Fan Speed Control Relay.

• If the test lamp illuminates

11. Ignition OFF, install all of the previously removed KR20 Cooling Fan Relays. Disconnect the harness connector at the G10 Cooling Fan Motor, ignition ON.

12. Command the cooling fan ON at high speed with a scan tool.

13. Verify a test lamp illuminates between ground and each of the G10 Cooling Fan Motor circuit terminals listed below:

* G10 Cooling Fan low speed circuit terminal 2

* G10 Cooling Fan medium speed circuit terminal 3

* G10 Cooling Fan high speed circuit terminal 4

• If the test lamp does not illuminate at each terminal

1. Ignition OFF, remove the test lamp.

2. Disconnect the appropriate relay from the list below:

* KR20C Cooling Fan Low Speed Relay

* KR20D Cooling Fan High Speed Relay

* KR20P Cooling Fan Medium Speed Relay

3. Test for less than 2 ohms in the relay controlled output circuit, end to end.

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

• If less than 2 ohms, test or replace the relay.

• If the test lamp illuminate at each terminal

14. Test or replace the G10 Cooling Fan Motor.

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. 95-135 ohms for the KR20F Cooling Fan Relay.

• If less than or greater than the specified range
Replace the KR20 Cooling Fan Relay.

• If within the specified range

4. Test for infinite resistance between the following terminals:

* 30/3 and 86/1

* 30/3 and 87/5

* 30/3 and 85/2

* 85/2 and 87/5

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

• If infinite resistance

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

6. Install a jumper wire between relay terminal 86/1 and ground.

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

• If 2 ohms or greater
Replace 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 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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