Cooling Fan Always On

Cooling Fan Always On (2.4)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Circuit/System Description

The engine control module (ECM) grounds the low speed relay, which is relay 1, and the high speed relay, which is relay 2, control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the ECM detects that the actual state of the control circuit does not match the expected state, a DTC will set.


Reference Information
Schematic Reference

Engine Cooling Schematics (LE5) (Electrical Diagrams)Engine Cooling Schematics (LNF) (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cooling Fan Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Verification

1. If DTCs P0480 or P0481 are set, perform those diagnostics first.
2. Ignition ON, command each relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.



Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.



1. Ignition OFF, disconnect the affected relay.
2. Ignition OFF, connect a 30A fused jumper between the positive terminal at the battery and the fan voltage supply circuit terminal and verify fan activation.

* Cooling Fan Relay 1 = Terminal 87
* Cooling Fan Relay 2 = Terminal 30


• If the fan does not activate, test the fan voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the fan ground circuit for an open/high resistance. If the fan does not activate and the circuits test normal, replace the fan.

3. Ignition ON, connect a 30A fused jumper from the relay switch voltage supply circuit terminal to the fan voltage supply circuit terminal and verify fan activation.


For the Relay Switch Voltage Supply Circuit
* Cooling Fan Relay 1 = Terminal 30
* Cooling Fan Relay 2 = Terminal 87



For the Fan Voltage Supply Circuit
* Cooling Fan Relay 1 = Terminal 87
* Cooling Fan Relay 2 = Terminal 30


• If the fan does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance.
• If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.

4. If the fan and all circuits test normal, replace the faulty relay.



Repair Instructions

Cooling Fan and Shroud Replacement (Service and Repair)


Repair Verification

Ignition ON, command the relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.