(6) Trouble diagnosis: The electronic devices of the intake air pressure sensor can diagnose
such troubles as open/short circuit and the damage of senor. When the ECU detects that the
signal output by the sensor is beyond its normal signal curve, the sensor will be in trouble. For
example, when the intake air pressure is higher or lower than its limit, the ECU will confirm that the
sensor is in trouble (The pressure lower than the limit at start will be excluded by the ECU.), then
the engine MIL will be lighted and the operation under trouble mode will be applied.
2. Throttle position sensor figure (Fig. 1-3)
Fig. 1-3
(1) Function: To provide throttle-alternator position information to the ECU. According to this
information, the ECU can obtain other information on engine load, working condition (start, idle
speed, backing, partial load, and full load), acceleration and deceleration. With the three-wire
sensor, the ECU can detect the opening of throttle through the change of pressure.
(2) Structure and principle: As an angle sensor with linear output, the sensor is made by two arc
sliding contact resistances and two sliding contact arms. The turning shaft of the sliding contact
arm shares the same axis with the throttle shaft. Power supply voltage (US) of 5V is added to the
both ends of the sliding contact resistance. When the throttle turns, the arm turns and moves on
the sliding contact resistance. Then, the electric potential (UP) at the contact point will be led out
as an output voltage. Actually, it is an angle sensor and the real value adopted by the ECU is the
value of Up/Us, and the value fluctuation of the sensor caused by the fluctuation of the generator
voltage will be avoided.
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