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 seconds. 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.