Circuit Description

Throttle Position (TP) sensor uses 2 sensors which detects throttle opening and a malfunction of the TP sensor. TP sensor provides an input voltage of 0-5 volts to VTA and VTA2 terminals at Engine Control Module (ECM) in proportion to throttle opening. ECM uses input signals and controls the throttle control motor to provide proper throttle valve opening in response to driving conditions. DTC is set after vehicle speed exceeds 19 MPH and improper input signals from TP sensor are received at ECM. If DTC P0121 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. Possible cause is defective TP sensor.