Throttle Body Assembly

Fig 1: Identifying Throttle Body Assembly Components

Courtesy of GENERAL MOTORS CORP.

The throttle body functions similar to a conventional throttle body with the following exceptions:

• An electric motor opens and closes the throttle valve.
• The TAC module is an integral part of the throttle body assembly.
• The throttle valve is spring loaded and the default position is slightly open.
• The throttle position (TP) sensor is integral to the TAC module assembly.

The TP sensor signals are used to determine the throttle plate or throttle valve angle. The TP sensor outputs provide the powertrain control module (PCM) with a signal voltage that is proportional to the throttle plate movement. The TP sensor is actually a Hall Effect switch. The Hall Effect switch is surrounded by a magnetic yoke that induces a flux in the magnetic field when the throttle shaft is rotated. An integrated circuit (IC) receives and converts the magnetic pulses into two separate TP signal, each with their own characteristics. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens. TP sensor 1 determines the actual throttle valve position. TP sensor 2 has a voltage that is more than twice that of TP sensor 1 at idle. TP sensor 2 provides a backup value for TP sensor 1.