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 3 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 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 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 [1][2]Cooling System
Connector End View Reference
* Component Connector End Views Fuel Pump and Level Sensor Assembly
* Electrical Center Identification Views X50A Fuse Block - Underhood X4
Description and Operation
Cooling Fan Description and Operation Cooling Fan
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 (LFX) Scan Tool Testing and ProceduresEngine Control Module Scan Tool Information (LUK) 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 fans turn ON and OFF when changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect all of the KR20 Cooling Fan Relays.
Note: The jumper wire completes the ground circuit for the right fan. Leave this jumper in place until instructed.
2. Connect a 30 A fused jumper between the KR20E Cooling Fan Speed Control Relay switch circuit terminal 5 and the ground circuit terminal 3.
Note: The following test must be performed on both the high speed fan relay circuit and the low speed fan relay circuit.
3. Ignition ON, verify that a test lamp illuminates between ground and the relay switched B+ circuit terminal listed below:
* KR20C Cooling Fan Low Speed Relay terminal 30
* KR20D Cooling Fan High Speed Relay terminal 5
• If the test lamp does not illuminate, test the appropriate relay switch 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 appropriate G10 Cooling Fan Motor.
Note: The following test must be performed first on the Left high speed fan relay circuit and next on the low speed fan relay circuit. Leave the jumper connected to the low speed fan relay circuit for the remainder of this procedure.
4. Connect a 30 A fused jumper between the KR20 Cooling Fan Relay circuit terminals listed below. Verify the appropriate fan is activated.
* KR20D Cooling Fan High Speed Relay terminals 5 and 3
* KR20C Cooling Fan Low Speed Relay terminals 30 and 87
• If the corresponding cooling fan does not activate, test the relay controlled output circuit and the cooling fan ground circuit for an open/high resistance. If the circuits tests normal, replace the appropriate G10 Cooling Fan Motor.
• If the corresponding cooling fan activates, replace the appropriate KR20 Cooling Fan Relay.
5. Remove the jumper wire from the KR20E Cooling Fan Speed Control Relay cavity.
6. Install the KR20E Cooling Fan Speed Control Relay. Verify both fans activate at low speed.
• If both fans do not activate, test the relay controlled output circuit terminal 4 of the KR20E Cooling Fan Speed Control Relay for a short to ground or an open/high resistance.
7. If the circuits test normal, test or replace the KR20E Cooling Fan Speed Control 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. Test for infinite resistance between the terminals listed below:
* 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 Cooling Fan Speed Control Relay only.
4. Test for less than 2 ohms between terminals 30 and 87A.
• If greater than the specified range, replace the KR20E Cooling Fan Speed Control 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. Test for infinite resistance between the terminals listed below:
* 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 KR20E Cooling Fan Speed Control Relay only.
4. Test for less than 2 ohms between terminals 3 and 4.
• If greater than the specified range, replace the KR20E Cooling Fan Speed Control 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)
* Engine Coolant Fan Motor Replacement Service and Repair