The TAC module is the 'Control Center' for the electronic throttle system. The Module is also located on the accelerator pedal assembly. 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 it to the actual throttle position. This is accomplished by monitoring the APP and the TP sensor. These two 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.