Edmunds Answers



  • MrShift@Edmunds 11/14/11 12:29 pm PST

    The computer senses that the fan is running faster than it should for the conditions noted. Might be some stuck valve in the clutch assembly ?? Not sure what the effects would be--maybe more noise, less MPG?

    Here's how it works:

    Circuit Description
    The cooling fan relay sends a Pulse Width Modulation (PWM) signal of 12-14 volts to the cooling fan through the cooling fan clutch supply voltage circuit. The Powertrain Control Module (PCM) uses this PWM signal in order to control the speed of the cooling fan. The signal controls the position of the oil control valve inside the cooling fan clutch. If the cooling fan RPM is different than the PCM is expecting, DTC P1484 will set. The actual cooling fan RPM vs the desired cooling fan RPM is not always exactly the same. There can be up to an 800-RPM difference.

    Conditions for Running the DTC

    • The engine is running.
    • The system voltage is greater than 8.5 volts.
    • The Intake Air Temperature (IAT) is greater than -7°C (19°F) .
    • DTCs P1481 and P1482 are not set.
    • The engine speed is less than 3200 RPM.
    • The engine speed is not changing more than 250 RPM for 5 seconds.
    • Fan command is greater than 0%.

    Conditions for Setting the DTC

    • The maximum allowable error of 1000 RPM in the cooling fan speed occurs for 100 seconds.
    • The PCM detects that the cooling fan clutch is locked up.

    Action Taken When the DTC Sets

    • The Reduced Engine Power indicator illuminates only if the PCM detects that the cooling fan clutch is locked up.
    • The PCM illuminates 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 conditions as Freeze Frame/Failure Records data.
    • A history DTC is stored.
    • The PCM commands the cooling fan to 100%.

    Conditions for Clearing the MIL/DTC

    Important: Follow this procedure in order to clear DTC P1484 after completing a repair.

    1. Use the Clear DTC Information function on the scan tool.
    2. Perform an ignition key cycle. 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.

    Diagnostic Aids

    • An inline connector could cause an intermittent DTC. Ensure to test for poor connections and pin retention at all inline connectors. If the condition is not present, refer to Testing for Intermittent and Poor Connections.
    • Disconnect the harness connector of the cooling fan from the shroud. Inspect the exposed wires between the harness connector and the tubing.
    • If DTCs P1484 and P0113 are set, and the weather conditions are cold, the cooling fan code may be false. Clear DTC P1484, and after an IAT sensor check, allow the DTC to reset.

    Test Description
    The numbers below refer to the step numbers on the diagnostic table.

    1. This step ensures that the DTC has failed this ignition cycle. If the scan tool displays Passed, then the answer is No.
    2. The cooling fan noise should increase as the cooling fan engages. It can take up to 2 minutes for full cooling fan engagement. If cooling fan is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, then answer Yes.
    3. In the previous step the cooling fan was fully engaged. This step tests to ensure that the cooling fan will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan and a disengaged cooling fan. The cooling fan is completely disengaged when the excessive fan noise is not heard.
    4. Tests the PCM's ability to control the cooling fan. If answer to question is Yes, ensure to refer to all Diagnostic Aids.
    5. Inspect for a mechanical condition which causes the DTC to set.
    6. Tests for voltage on the cooling fan clutch supply voltage circuit of the cooling fan. The cooling fan connector is a seal connector. You must use jumper wires for testing or damage to wiring or connector could happen.
    7. Tests the cooling fan relay for a PWM signal on the cooling fan clutch supply voltage circuit of the cooling fan.

    Also, here's some testing you can do if you're mechanically inclined:


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