The APS(Accelerator Pedal Sensor) is a very important sensor which controls the fuel amount by transmitting the driver's accelerating intention to the ECM. The APS 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.