P1482

DTC P1482
Circuit Description
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 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 effected by many different conditions and can be adjusted from 10 percent to 90 percent duty cycle (PWM), 90 percent is considered high speed fan. When multiple cooling fan speed requests are received the ECM uses the highest cooling fan speed of all the requests. During normal operation the control circuit voltage will be low and near battery voltage when OFF.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1482 Cooling Fan Speed Output Circuit

Conditions for Running the DTC
^ The ignition voltage is between 10 - 18 volts.
^ The engine speed is more than 400 RPM.

Conditions for Setting the DTC
The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match.

Action Taken When the DTC Sets
^ The ECM will illuminate the malfunction indicator lamp (MIL) ON the second consecutive ignition cycle that the diagnostic runs and fails.
^ The ECM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC
^ The ECM will turn OFF the MIL during the third consecutive ignition cycle that the diagnostic runs and passes.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ Use the scan tool Clear DTC Information function.

Diagnostic Aids
Refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. The engine must be running to control the cooling fan using the scan tool.
5. When testing this circuit the red lead of the DVOM must be connected to battery positive voltage.
6. This step tests the cooling fan motor for operation.

Step 1 - Step 10:

Step 11 - Step 16: