P0481

DTC P0480, P0481, P0691, P0692, P0693, or P0694

Circuit Description

The engine control module (ECM) controls the low speed cooling fan operation by grounding the low speed fan relay control circuit with an internal solid state device called a driver. For high speed cooling fan operation, the ECM grounds the high speed and S/P relay control circuit at the same time the low speed control circuit is grounded. Battery positive voltage is supplied to the low speed, high speed and S/P fan relays. When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage potential of the control circuit should be high, near battery voltage.

The ECM monitors the relay control circuits for the following conditions:

* Short to ground
* Short to voltage
* An open circuit

If the ECM detects an improper voltage level on the low or high speed driver circuits, then code P0480, P0481, P0691, P0692, P0693, or P0694, will set and the effected driver will be disabled.

* Cooling fan relay 1 control circuit refers to the low speed cooling fan relay
* Cooling fan relay 2 control circuit refers to the high speed cooling fan relay

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC P0480 Cooling Fan Relay 1 Control Circuit
* DTC P0481 Cooling Fan Relay 2 Control Circuit
* DTC P0691 Cooling Fan Relay 1 Control Circuit Low Voltage
* DTC P0692 Cooling Fan Relay 1 Control Circuit High Voltage
* DTC P0693 Cooling Fan Relay 2 Control Circuit Low Voltage
* DTC P0694 Cooling Fan Relay 2 Control Circuit High Voltage

Conditions for Running the DTC

* The ignition voltage is between 8-18 volts.
* The engine speed is more than 40 RPM.
* The ECM driver transitions from ON to OFF or from OFF to ON.

Conditions for Setting the DTC

P0481

The ECM detects an open circuit on the high speed cooling fan relay control circuit.

P0693

The ECM detects a short to ground on the high speed cooling fan relay control circuit.

P0694

The ECM detects a short to voltage on the high speed cooling fan relay control circuit.

The above condition is present for one second.

P0480

The ECM detects an open on the low speed cooling fan relay control circuit.

P0691

The ECM detects a short to ground on the low speed cooling fan relay control circuit.

P0692

The ECM detects a short to voltage on the low speed cooling fan relay control circuit.

Action Taken When the DTC Sets

* The ECM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
* 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 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.
* Use the scan tool Clear DTC Information function.

Diagnostic Aids

* Review the Freeze/Failure Records vehicle mileage since the diagnostic test 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 low speed fan relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Listen for an audible click when the S/P and high speed fan relays operate. Command both the ON and OFF states. Repeat the commands, as necessary.

Step 1 - Step 8:

Step 9 - Step 19:

Step 20 - Step 21: