Cooling Fan Always On
Cooling Fan Always On
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 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
* Certain resistance conditions with IAT or ECT sensors may cause unwarranted cooling fan activation. If the ECM is commanding the cooling fans ON for no apparent reason and without any component or system DTCs set, the IAT or ECT sensor may be skewed. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor Temperature Versus Resistance - Engine Coolant Temperature Sensor or Temperature Versus Resistance - Intake Air Temperature Sensor (Hitatchi Sensor) Temperature Versus Resistance - Intake Air Temperature Sensor (Hitatchi Sensor) if this condition is suspected.
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, observe the scan tool parameters listed below. Verify that both parameters display OFF.
* Cooling Fan Relay 1 Command
* Cooling Fan Relays 2 and 3 Command
3. Ignition ON, observe that the G10 Engine Cooling Fans are not ON.
Circuit/System Testing
Note: The following tests must be performed on each cooling fan relay.
1. Ignition OFF, disconnect each KR20 Cooling Fan Relay one at a time.
2. Ignition ON, observe that the cooling fans are not activated.
• If the fans are activated, test for a short to voltage in the relay controlled output circuit of the appropriate cooling fan.
• If the fans are not activated, test or replace the appropriate KR20 Cooling Fan 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 repair.
Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)