CTS V8-5.7L VIN P (2004)
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The APP is actually 3 individual accelerator pedal position
sensors within 1 housing. Three separate signal, low reference, and 5-volt reference circuits are used in order to connect the APP and the TAC
module. The APP sensor 1 voltage should increase at the same time that the accelerator pedal is depressed, from below 1 volt at 0 percent pedal
travel to above 2 volts at 100 percent pedal travel. APP sensor 2 voltage should decrease from above 4 volts at 0 pedal travel to below 2.9 volts at
100 percent pedal travel. APP sensor 3 voltage should decrease from above 3.8 volts at 0 pedal travel to below 3.1 volts at 100 percent pedal travel.
Throttle Body Assembly
The throttle body for the TAC system is similar to a conventional throttle body with some exceptions. One exception is the use of a motor to control
the throttle position (TP) instead of a mechanical cable. The other exception is the new design TP sensor. The TP sensor mounts on the side of the
throttle body opposite the throttle actuator motor. The TP sensor is actually 2 individual TP sensors within 1 housing. Separate low reference and
5-volt reference circuits are used in order to connect the TP sensors and the TAC module. The TP sensor 1 signal voltage increases at the same time
that the throttle opens. The voltage increases, from approximately 1 volt at 0 throttle to above 3.5 volts at 100 percent throttle. TP sensor 2 signal
voltage decreases at the same time that the throttle is opened. The voltage increases from approximately 3.8 volts at 0 throttle to below 1 volt at 100
percent throttle.
Throttle Actuator Control (TAC) Module
The TAC module is the control center for the electronic throttle system. The TAC module and the PCM communicate via a dedicated redundant serial
data circuit. The TAC module and the PCM monitor the commanded throttle position and compare the commanded position to the actual throttle
position. This is accomplished by monitoring the APP and the TP sensor. These 2 values must be within a calibrated value of each other. The TAC