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Cooling Fan Always On (LAU)

Cooling Fan Always On (LAU)

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


Circuit/System Description

The engine control module (ECM) commands the cooling fan ON depending on the engine cooling requirements. The ECM controls the cooling fan speed by commanding the cooling fan control module. The cooling fan control module supplies the power and ground circuits for the cooling fan. The ECM sends a pulse width modulated (PWM) signal voltage to the cooling fan control module. The cooling fan control module interprets the signal and operates the cooling fan at the commanded speed.

Diagnostic Aids

The ECM has the capability of providing command to the fan module even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know when the fan is being commanded ON by the ECM.

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling Fan Description and Operation (LF1, LFW, LFX) Cooling Fan Description and Operation (LAU)

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification


1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0480, P0691, or P0692, is not set.

2. If a DTC is set, refer to DTC P0480, P0691, or P0692 (LAU) .

3. Ignition ON, observe the scan tool Cooling Fan Motor Command parameter. The parameter should display 0 %.

4. Ignition ON, observe that the engine cooling fan is not operating.

5. If the fan is operating, replace the K22 cooling fan control module.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Engine Coolant Fan Replacement (LAU) ; Engine Coolant Fan Replacement (LF1, LFW or LFX)

• Control Module References