P0481

DTC P0481





Circuit Description
Battery positive voltage is supplied to the cool fan mode relay and the cool fan 2 relay from the battery. The powertrain control module (PCM) controls the relays by grounding the high speed cooling fan relay control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line, which is monitored by the PCM.When the PCM is commanding a component on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.
The PCM will monitor the control circuit for the following:
- A short to ground
- A short to voltage
- An open circuit
When the PCM detects any of the above conditions, the DTC will set and the affected driver will be disabled.

Conditions for Running the DTC
- The ignition voltage is between 9.0 - 18.0 volts
- The engine speed is greater than 80 RPM.
- The PCM driver transitions from ON to OFF or from OFF to ON.

Conditions for Setting the DTC
- An improper voltage level has been detected on the high speed cooling fan relay control circuit.
- The above conditions are present for at least 30 seconds.

Action Taken When the DTC Sets
- The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
- The PCM will store conditions, which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
- The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
- The DTC can be cleared by using the scan tool.

Diagnostic Aids
Check for the following conditions:
- A faulty connection at the PCM, inspect the harness connectors for the following conditions.
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Faulty terminal to wire connections
- Inspect the wiring harness for damage.
- If the harness appears to be OK, disconnect the PCM, turn the ignition ON and observe a digital multimeter (DMM) connected between the high speed cooling fan relay control circuit and ground at the PCM harness connector. While moving connectors and the wiring harness related to the cool fan mode and the cooling fan 2 relays, a change in voltage will indicate the location of the fault.
Review the Freeze/Failure Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the cooling fan mode and the cooling fan 2 relays operate. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for voltage at the coil side of the cooling fan 2 relay. The cool fan 2 fuse supplies power to the coil side of the cool fan 2 relay.
4. Verifies that the PCM is providing ground to the cool fan 2 relay.
5. Tests if ground is constantly being applied to the cool fan 2 relay.