P0121 KIA - Throttle Position Sensor Circuit Range/Performance Problem
- Throttle position sensor harness is open or shorted
- Throttle position sensor circuit poor electrical connection
- Faulty Engine Control Module (ECM)
Throttle Position (TP) Sensor measures the opening angle of throttle valve and mounts on the side of the throttle body and is connected to the throttle blade shaft. The TP sensor’s resistance changes according to the throttle blade shaft position. TP Sensor has a potentiometer whose resistance changes along with the Throttle valve position. The Engine Control Module (ECM) provides a 5volt reference voltage to the TP Sensor. The ECM reads the voltage across the TP Sensor and converts it into throttle position. During acceleration, the TP Sensor resistance decreases. During deceleration, the TP Sensor resistance increases. The ECM uses the TP Sensor signal to adjust timing and injector pulse width. The TP Sensor signal along with the MAF sensor signal is used by the ECM to calculate engine load. Throttle angle information to the ECM to be used for the detection of engine status such as idle, part load, full throttle condition and anti-jerk condition and acceleration fuel enrichment correction.