DTC P2123: Throttle/Pedal Position Sensor/Switch 'D' Circuit High Input: General Description

The APS is a very important sensor which controls the fuel amount by transmitting the driver's accelerating intention to ECM. And it is divided into APS 1, 2 because its reliability is important. The APS 1, 2 are composed with the independent power and ground. APS 2 shows the 1/2 output of the APS1 and decides the fault if the ratio of APS 1, 2 is different. When the APS 1 is out of order, the signal of APS 2 can be substituted instead of APS 1 and vise versa.