Cooling Fan Inoperative 2.0

The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated (PWM) signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the engine cooling fan motor in relation to the pulse width modulated signal. The cooling fan speed can be adjusted from 10 percent to 90 percent duty cycle. 90-94 percent is considered high speed fan.

The ECM monitors the voltage on the cooling fan speed control circuit driver output. Voltage is near B+ when the driver is OFF, and near ground when the driver is ON. If the difference between the actual and expected voltage exceeds a calibrated value, a DTC will set.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. If DTCs P0480, P0691, or P0692 are set, perform that diagnostic first.
2. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
3. Ignition ON, command the cooling fan speed from 10-90 percent with a scan tool. The fan speed should transition with the commanded states.

Important: The Circuit/System Verification must be performed first or misdiagnosis may result.

1. Ignition OFF, disconnect the cooling fan.
2. Ignition OFF, measure between ground and the cooling fan ground circuit terminal 2 at the engine harness connector for less than 1 ohm of resistance.

⇒	If more than 1 ohm, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the cooling fan voltage supply circuit terminal 1 and ground. The lamp should illuminate.

⇒	If the lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, replace the cooling fan assembly.

4. If all circuits test normal, replace the cooling fan assembly.

1. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, command the cooling fan speed from 10-90 percent with a scan tool. The fan speed should transition with the commanded states.