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Category: Check Engine Light Repair and Diagnostic Help

The throttle position (TP) sensor is used by the powertrain control module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with three circuits: a 5-volt reference, a low reference, and a signal. The PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit.

Rotation of the TP sensor rotor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to greater than 4 volts through the TP sensor signal circuit. When the conditions for running this DTC are met the PCM will use the manifold absolute pressure (MAP) sensor to determine if the predicted operating range of the TP Sensor is correct. A skewed MAP Sensor may cause DTC P0121 to set and should be tested for proper operation if the TP sensor is determined to be operating properly and this DTC continues to set.

Rotation of the TP sensor rotor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to greater than 4 volts through the TP sensor signal circuit. If the PCM detects an excessively low signal voltage, DTC P0122 will set.

If the PCM detects an excessively high signal voltage, DTC P0123 will set.

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  • Guest - manually check

    My engine check light sometimes goes on and off. When the light stay on engine runs perfect, but the time come to light off the engine run quiet ok & when come to stop engine run off.

  • Guest - Tech

    In reply to: Guest - manually check

    My engine check light sometimes goes on and off. When the light stay on engine runs perfect, but the time come to light off the engine run quiet ok & when come to stop engine run off.
    <br />You would first need to get the codes scanned from the computer. Then we would know what system is having a problem. Most of the large national parts store chains will do this for free.