Circuit Description

Throttle Position (TP) sensor is a variable resistor located on throttle body which monitors throttle opening and delivers input signal to VTA terminal on ECM. Input signal is about .3-1.0 volt with throttle fully closed and about 3.2-4.9 volts with throttle fully open. ECM uses input signal for determining vehicle driving conditions and adjusts air/fuel mixture accordingly. DTC is set when ECM consistently detects less than .1 volt or more than 4.9 volts on VTA circuit for more than .5 second. If DTC P0120 exists, ECM will operate in fail-safe mode. Possible causes are:

• TP sensor circuit is open or shorted.
• Defective TP sensor.
• Defective ECM.