A80 BT Intelligent Diagnosis System
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up the dead point is in the compression stroke and then in the firing or
exhaust stroke. This information is not available from the crankshaft
position during starting. In contrast, the information generated by the
crankshaft sensor is sufficient to determine the engine state while the
vehicle is running. That is to say, the ECU still knows the engine state
when the camshaft speed sensor fails during vehicle operation.
The camshaft speed sensor uses the Hall Effect to determine the
position of the camshaft. The Hall Effect is as follows: A tooth made of
ferromagnetic material is placed on the camshaft, and the teeth rotate
with the camshaft. When the semiconductor wafer through which the
current flows in the camshaft rotational speed sensor passes the tooth, the
magnetic field of the sensor deflects the flow of electrons on the
semiconductor wafer perpendicular to the direction of the current. Thus,
a voltage signal (Hall voltage) is formed in a short time, and this signal
informs the ECU that the first cylinder is in the compression stroke.
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3
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Temperature sensor
The temperature sensor is used in several places:
○
1
in the cooling
water circuit to infer the engine temperature from the cooling water
temperature;
○
2
used in the intake port to determine the temperature of
the intake air;
○
3
used in the oil to determine Oil temperature (optional);
○
4
used in the fuel return oil line to determine the fuel temperature