The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include the following:
Each of these components interface together to ensure accurate calculations and control of the throttle position.
The APP sensor is mounted on the accelerator pedal assembly. The APP is actually 3 individual accelerator pedal position sensors within one housing. Three separate signal, low reference, and 5.0-volt reference circuits are used to connect the APP and the TAC module. The APP sensor 1 voltage should increase as the accelerator pedal is depressed, from below 1.0 volt at 0 percent pedal travel to above 2.0 volts at 100 percent pedal travel. APP sensor 2 voltage should decrease from above 4.0 volts at 0 percent 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 percent pedal travel to below 3.1 volts at 100 percent pedal travel.
The throttle body for the TAC system is similar to a conventional throttle body with a couple of exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. The other exception is the new design throttle position (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 one housing. Separate signal, low reference, and 5.0-volt reference circuits are used to connect the TP sensors and the TAC module. The TP sensor 1 signal voltage increases as the throttle opens, from around 1.0 volt at 0 percent throttle to above 3.5 volts at 100 percent throttle. TP sensor 2 signal voltage decreases as the throttle is opened, from around 3.8 volts at 0 percent throttle to below 1.0 volt at 100 percent throttle.
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 throttle position (TP) sensor. These 2 values must be within a calibrated value of each other. The TAC module also monitors each individual circuit of the TP sensor and the APP to verify proper operation.
