Cooling Fan Always On (Dual Fan)

Cooling Fan Always On (Duel Fan)

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 the Fan Low relay, and the high speed relay, which is the Fan High 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. 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 (Electrical Diagrams)
Connector End View Reference

* Master Electrical Component List (Component Locations)
* 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)
* 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 P0691, P0692, P0693 or P0694 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 fans are not activated.

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




Repair Instructions

* Engine Coolant Fan Motor Replacement (Service and Repair)
* Control Module References (Programming and Relearning)



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.