Cooling Fan Always On

Cooling Fan Always On (LAT-2.4L)

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy 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 the AUX fan relay, and the high speed relay, which is the main fan relay, 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.


Reference Information
Schematic Reference

Engine Cooling Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cooling Fan Description and Operation (LAT-2.4L) (Description and Operation)Cooling Fan Description and Operation (Except LAT-2.4L) (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)
* Electrical Center Identification Views (Application and ID)

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, then perform those diagnostics first.
2. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
3. Ignition ON, observe that the fan is not activated.



Circuit/System Testing

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



1. Ignition OFF, disconnect the relays.
2. Ignition ON, observe that the fan is not activated.

• If the fan is not activated, replace the faulty relay.
• If the fan is activated, test the fan voltage supply circuits for a short to voltage.




Repair Instructions

* Cooling Fan and Shroud Replacement (LAT-2.4L) (Service and Repair)Cooling Fan and Shroud Replacement (LE5 2.4L, LZ4-3.5L, LY7 3.6L) (Service and Repair)
* Engine Control Module Replacement (LE5 2.4L) (Service and Repair)Engine Control Module Replacement (LAT-2.4L) (Service and Repair) for the 2.4L engine



Repair Verification

1. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, observe that the fan is not activated.