The electronic throttle body can automatically open or close the throttle according to the
driver’s will to apply the accelerator pedal to let the engine work under the corresponding operating
mode. The electronic throttle has cancelled the conventional throttle guy and the opening of throttle
is controlled by ECU based on the signal from accelerator pedal and other signals (such as A/C,
power assisted steering, back and gearshift etc.) through an electronic step motor inside the
electronic throttle body. In addition to cancel of conventional idle speed by-pass and idle speed step
motor, there are also throttle position sensors on the electronic throttle body to feed back the opening
of the throttle. This suite of throttle position sensor is different from the common one; totally two
suites of throttle position sensors are installed inside the electronic throttle body to monitor
rationality of the signals from the latter; when any problem occurs in a certain signal, ECU can still
use the other suite of signals to work on.
6.2 Working principle:
The throttle driving motor is a micro motor, which is composed of multi steel stators in a circle
and a rotor, with one coil on each steel stator. The rotor is a permanent magnet with a nut at its center.
All stators coils are constantly power on. As long as the direction of current of one coil is changed,
the rotor will turn a certain angle. When the directions of current of all stator coils is changed in a
proper order, a rotating magnetic field is formed, which will drive the rotor made from permanent
magnet rotate along a certain direction. Its principle is just that of a micro direct current motor.
This motor drives a suite of special gear reducing mechanism and a bidirectional spring; when
the system is under power off condition, this mechanism can ensure that the opening of throttle valve
plate maintains at a safe position where is bigger than that for idle speed but not too high, so that the
vehicle can continue to run; if engine ECU has entered this failure mode, when applying the
accelerator pedal, the valve plate of the electronic throttle body will no longer act.
6.3 Failure diagnosis:
ECU can monitor short-circuit and break of coil of the throttle driving motor, and light the engine
failure light in case of such failure to let the engine enter failure mode, when the engine fails to
accelerate, has very poor driving performance and needs maintenance immediately.
7. Oxygen Sensor
7.1 Function of the sensor:
Oxygen sensor is one of the principal sensors on modern autos; it can feed back the mixture
strength by detecting oxygen content in exhaust gas. ECU will correct the mixed gas based on the
Electronic throttle
