The engine cooling fan is a variable speed fan. The engine control module (ECM) controls the fan speed by sending a pulse width modulated signal to the cooling fan speed 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 is affected by many different conditions and can be adjusted from 10 to 84 percent duty cycle (PWM). A duty cycle of 84 percent is considered high fan speed. When multiple cooling speed requests are received the ECM uses the highest cooling fan speed of all the requests. During normal fan ON operation the control circuit voltage will be low and near battery voltage when the fan is OFF.

DTC P0480 is Type B DTC.

DTC P0480 is Type B DTC.

1. Cooling fan duty cycle starts when engine coolant temperature reaches approximately 95°C (204°F) and reaches high speed at temperatures above 113°C (235°F).
2. Cooling fan duty cycle starts when A/C pressure reaches approximately 1100 kPa (160 Psi) and reaches high speed at A/C pressures above 2480 kPa (360 psi).
3. At engine oil temperatures above approximately 150°C (302°F) the cooling fan duty cycle will be commanded to high speed.
4. At transmission oil temperatures above approximately 132°C (270°F) the cooling fan duty cycle will be commanded to high speed.
5. After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 113°C (235°F) or the A/C pressure is greater than 1720 kPa (249 psi) the cooling fan duty cycle is set to 50 percent, low speed. If the coolant temperature drops below 110°C (230°F) and the A/C pressure drops below 1660 kPa (241 psi) the fan will shut OFF. The fans will automatically shut OFF after 2 min. regardless of coolant temperature.

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. Ignition ON, increase and decrease the cooling fan ON and OFF with a scan tool. Observe that the cooling fan operates with each command.
2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

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

1. Ignition OFF, disconnect the engine harness connector from the cooling fan speed control module.
2. Ignition OFF, install a test lamp between the cooling fan speed control circuit terminal X3 49 and B+. The lamp should be OFF.

⇒	If the lamp is ON, test the cooling fan speed control circuit for a short to ground. If the circuit tests normal, replace the ECM.

3. Ignition ON, command the cooling fan ON with a scan tool. The lamp should be ON.

⇒	If the lamp is OFF, test the cooling fan speed control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Ignition OFF, disconnect the cooling fan harness connector at the cooling fan speed control module.
5. Connect a jumper wire between the fan ground circuit terminal 1 and ground. Connect a 30A fused jumper wire between the positive terminal at the battery and the fan voltage supply circuit terminal 4 and verify fan activation.

⇒	If the cooling fan does not activate, replace the cooling fan.

6. Ignition OFF, measure between the cooling fan speed control module ground circuit terminal 2 at the harness connector and ground for less than 1 ohm.
7. Install appropriately fused jumpers in the power and ground circuits between the cooling fan speed control module harness connector terminals and the cooling fan harness connector terminals. The fan should activate at full speed.

⇒	If the fan does not activate correctly, test the cooling fan speed control module 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 speed control module.

8. If the ECM, fan, and all circuits test normal, replace the cooling fan speed control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming