Feb 112015
 

I have little to no power under 2,000rpms but from 2,500+ rpms drives fine (no idle issues or misfiring). I got a code P0123 yesterday. Check the TPS – the output on TP Sen 1 was good ( 0.5 – 4.7 v) but checked TP Sen 2 – I got no readings. Is this normal? I can not find anything on the ‘proper’ reading.

  One Response to “2008 Jeep Wrangler Unlimited X, 3.8l, auto”

  1. Yes it is normal. I recommend checking all connections first.
    If you want to check TP Sensor 2:
    >Connect a jumper wire between the (K922) TP Sensor Ground circuit and (K22) TP Signal 1 Signal Circuit.
    Tp Sensor 1 voltage should be between 4.7 volts to 0.3 volt.
    >For TP Sensor 2, connect jumper wire between (F855) 5-volt supply circuit and the (K122) TP signal 2 circuit.
    TP Sensor 2 voltage should change from approximately 0 volts to 5.0 volts.

    Verify that there is good pin to terminal contact in the Throttle Body and Powertrain Control module connectors. If OK, replace the Throttle Body Assembly.

    Reference:
    P0123 Jeep – Throttle Position Sensor/Accelerator Position Pedal Circuit High Input

    Possible causes
    – Faulty throttle position sensor
    – Throttle position sensor harness is open or shorted
    – Throttle position sensor circuit poor electrical connection
    – Faulty Powertrain Control Module (PCM)

    When is the code detected?
    The P0123 code will set if the monitored TPS volts rise above 4.8 volts for the period of 25 ms.

    P0123 Jeep Description
    The Throttle Position Sensor (TPS) responds to the accelerator pedal movement. This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the Powertrain Control Module (PCM). In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the PCM.

    Idle position of the throttle valve is determined by the PCM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch, which is built into the throttle position sensor unit, is not used for engine control.

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