DTC P2121 Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance: Fail-Safe

The accelerator pedal position sensor has 2 (main and sub) sensor circuits. If a malfunction occurs in either of the sensor circuits, the ECM detects the abnormal signal voltage difference between the 2 sensor circuits and changes to limp mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal opening angle to allow the vehicle to continue driving. If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal as being fully closed. In this case, the throttle valve remains closed as if the engine is idling.

If a "pass" condition is detected and the ignition switch is turned OFF, the fail-safe operation stops and the system returns to normal.