Circuit Description

The accelerator pedal position (APP) sensor is made up of 2 sensors that are housed inside one assembly. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the sensors. The 5-volt reference for APP sensor 1 is supplied from the same source in the ECM as the 5-volt reference for the mass air flow (MAF) sensor and the fuel tank pressure (FTP) sensor. The 5-volt reference for APP sensor 2 is supplied from the same source in the ECM as the 5-volt reference for the throttle position (TP) sensors. The 5-volt reference voltage for all of the sensors is supplied on separate ECM terminals, but the terminals are connected internally to the shared voltage supply. The APP sensor sends a signal from each of the sensors to the ECM indicating the accelerator pedal position. The ECM actuates the throttle plates based on this information. The APP sensor 1 signal voltage increases as the throttle opens, from about 0.4 volts at closed throttle to above 3.5 volts at wide-open throttle (WOT). The APP sensor 2 signal voltage also increases as the throttle opens, but at a slightly different rate. The APP sensor 2 signal voltage increases from about 0.2 volts at closed throttle to about 1.8 volts at WOT. The control module compares the signal of each of the APP sensors, when the pedal is not in the rest position. If the ECM detects the APP sensors are not within a predicted value from each other, DTC P2138 sets.