2003 Hyundai Elantra

2003 Hyundai ElantraI get a P1140 code – on my little code checker it says manufacturers control, but I see on the internet that this code is for a Intake air temperature – so whats the problem why does it say manufacturers control when it should be pointing me to the IAT sensor which is part of the MAF I guess…


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  1. P1140 Hyundai – Inlet Air Temperature Sensor Malfunction

    This is the correct information for that code. There are many different code checkers to choose from. Unfortunately yours is only providing generic code information instead of vehicle specific code information.

    The Intake Air Temperature (IAT) sensor is a variable temperature sensitive resistor. Sensor resistance will change based on air temperature. The higher the temperature, the lower the resistance. The Engine Management System (EMS) provides a reference voltage and monitors the voltage drop between a fixed value internal resistance and the sensor resistance. This is called a voltage divider circuit.

    IAT sensor values are used by the EMS to assist with the calculation of idle speed, fuel mixture and spark advance.

    Inaccurate voltages from the IAT sensor may affect pulse-width, idle quality and tail pipe emissions. Intermittent signals may cause hesitation, stumble and surging. If an IAT sensor failure accompanies an Engine Coolant Temperature (ECT) sensor failure cooling fan operation may also be affected.

    Some manufacturers’ incorporate the Intake Air Temperature (IAT) sensor as part of the Mass Air Flow (MAF) sensor, or air flow meter.

    The following symptoms can be caused by a faulty IAT sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit.

    •Extended crank time when the engine is cold
    •Poor fuel economy
    •Spark knock

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