DTC P2121: Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance [08/2015 - ]: Fail-Safe

The accelerator pedal sensor assembly has two (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 two sensor circuits and switches to limp mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal position to allow the vehicle to continue driving. If both circuits malfunction, the ECM regards the accelerator pedal as being fully released. 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.