P1481

DTC P1481

Circuit Description

The powertrain control module (PCM) uses the cooling fan speed signal in order to determine the actual fan speed in relation to the desired fan speed. The PCM uses the cooling fan speed signal in order to reduce the cooling fan noise and in order to maintain the powertrain cooling requirements. The PCM supplies power and ground to the clutch hall effect sensor of the cooling fan clutch. The hall effect sensor returns a signal pulse through the speed signal circuit in response to the reluctor track, which is located inside the fan clutch. If during operation, the PCM detects a loss of the cooling fan speed signal, DTC P1481 will set.


DTC Descriptor

This diagnostic procedure supports the following DTC:


DTC P1481 Cooling Fan Speed Sensor Circuit


Conditions for Running the DTC

* The engine is running.
* System voltage is greater than 8.5 volts.



Conditions for Setting the DTC

* The PCM has detected a loss of cooling fan speed signal.
* The above condition is present for at least 11 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 the condition as Freeze Frame/Failure Records data.
* The PCM commands the cooling fan clutch to 100 percent.



Conditions for Clearing the MIL/DTC

* The PCM turns OFF the MIL after the third consecutive trip that the diagnostic test has run and passed.
* The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
* Clear the DTC by using the Clear DTC Information function of the scan tool .



Diagnostic Aids

* An inline connector could cause an intermittent DTC. Ensure to test for poor connections and pin retention at all inline connectors. Refer to system schematics for connector and locations.
* If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections . Testing for Intermittent Conditions and Poor Connections
* Disconnect the harness connector of the cooling fan clutch from the shroud. Inspect the exposed wires between the harness connector and the tubing.
* Inspect the cooling fan clutch harness in order to ensure that the clutch supply voltage circuit is not shorted to the following circuits:

^ The 5-volt reference circuit
^ The cooling fan speed signal circuit
^ The low reference circuit

* DTC P1481 will set if the engine is started without the drive belt ON.



Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. This step tests for the proper operation of the clutch hall effect sensor.
3. This step tests for the proper operation of the 5-volt reference circuit and of the low reference circuit of the cooling fan.

Step 1-8:

Step 9-14: