The vehicle engine has a variable speed cooling fan, which is controlled by the ECM (Engine Control Module) employing a pulse width controlled signal that is sent to the Cooling Fan Speed Control Module. The latter module has changes in the voltage drop across the fan motor according to the pulse width modulated signal.
The cooling fan speed depends on certain factors and can be adjusted from 10 to 90% of the duty cycle. The 90% is considered the high fan speed. When multiple cooling speed requests are received, the ECM will use the highest speed for all of them. During proper fan operation, the control circuit voltage will be low at Power On and close to battery voltage when the fan is Off.
The P1481 OBDII diagnostic code setting occurs when the ECM detects that the cooling fan signal has been lost, either intermittently or completely.
The OBD2 P1481 fault code is stored by one of the following factors:
The cooling fan clutch assembly harness may be deficient.
The fan clutch assembly circuit may have damage to its connections, in turn causing a short or open circuit.
The fan clutch assembly could be defective.
Possible solutions of the DTC code P1481
The steps to follow to correct the DTC P1481 OBDII code are:
To start the diagnosis it is necessary to consult the Technical Service Bulletins.
Check the cooling fan clutch assembly circuit for any common damage to its wiring or connectors. If you discover corrosion, burns, or wear, make the appropriate corrections.
Measure the cooling fan clutch assembly circuit voltages and verify that they are within the levels indicated by the manufacturer's specifications. If you find inconsistencies in one of these readings, you should proceed with the respective repairs.
If you do not detect damage to the electrical components or connections, you should check the integrity of the fan clutch assembly. If you find any deficiencies in the fan clutch assembly, make the appropriate adjustments.