Fuel System > Engine Control System > P0481 Fan 2 Control Circuit Malfunction

General Description

When the ambient air temperature is warm or the airflow across the engine is low, the engine coolant temperature can become hot. If the coolant temperature becomes too hot, it is possible that the engine could be damaged. The purpose of activating the engine compartment ventilation fan is to help reduce the engine coolant temperature to a level that is not threatening to engine performance and maintains the airconditioning system pressure at safe levels.

Electric fan is responsible for causing air movement around the engine coolant radiator. The amount of air movement caused by the fan is controlled based on the Vehicle Speed, coolant temperature, A/C pressure status, A/C switch request status, and A/C clutch state. A duty cycle is determined based on these input parameters. This duty cycle corresponds to fan speed which correlates to the amount of air movement caused by the fan. The increased air movement enhances the heat exchanger function of the radiator in the confined space of the engine-compartment, thereby reducing the engine coolant temperature more quickly.

DTC Description

If the PCM detects short to ground, to battery or open circuit in the Cooling fan relay(high) , PCM sets P0481. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC Detecting Condition

Item

Detecting Condition

Possible cause

DTC Strategy

•	Output driver chip monitors an fault.

•	Poor connection

•	Open or short in Cooling fan relay(high)(Condenser fan relay #1,2)

•	Faulty Cooling fan relay(high)(Condenser fan relay #1,2)

•	Faulty PCM

EnableConditions

•	Engine Running

•	11V ≤ Ignition Voltage ≤ 16V

Threshold value

•	Open or short in the circuit

DiagnosisTime

•	Continuous

MIL On Condition

•	2 driving cycles

Schematic Diagram

Monitor DTC Status

Check DTC Status

(1)	Connect scantool to Data Link Connector(DLC).

(2)

IG "ON".

(3)	Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.

(4)	Read "DTC Status" parameter.

(5)

Is parameter displayed "Present fault"?

	▶ Go to "Terminal and Connector inspection" procedure.
	▶ Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Terminal And Connector Inspection

1.	Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Has a problem been found?

	▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
	▶ Go to " Power Circuit Inspection " procedure

Power Circuit Inspection

■ Check voltage

IG "OFF".

2.	Disconnect the Cooling fan relay(high)(Condenser fan relay #1,2).

3.	IG "ON" and ENG "OFF"

Measure the voltage between battery power supply terminals of the Cooling fan relay(high)(Condenser fan relay #1,2) harness connector and chassis ground.

Specification : B+

Is the measured voltage within specification ?

	▶ Go to "Control Circuit Inspection" procedure.
	▶ Check if cooling fan fuse is open or not installed. ▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.

Control Circuit Inspection

IG "OFF"

2.	Disconnect the cooling fan relay(high)(Condenser fan relay #1,2).

3.	IG "ON" & ENG "OFF"

Measure voltage between Fan Relay Control(High) terminal of the Cooling fan relay(high)(Condenser fan relay #1,2) harness connector and chassis ground.

Specification : Approx. 2.5V

Is the measured voltage within specifications?

▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.

There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others.

▶ Repair open or short in control circuit, and go to "Verification of Vehicle Repair" procedure.

Verification Of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

1.	Connect scantool and select "DTC" button.

2.	Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

3.	Read "DTC Status" parameter

Is parameter displayed "History(Not Present) fault"?

	▶ System performing to specification at this time. Clear the DTC
	▶ Go to the applicable troubleshooting procedure.