940 L4-2.3L SOHC VIN 88 B230F (1992)
Crankshaft Position/Engine Speed Sensor: Description and Operation
Crankshaft Position And Speed Sensor
PURPOSE AND LOCATION
The input signal for crankshaft position and engine speed is generated by the crankshaft position/speed sensor and sent to the ignition ECU (3).
From there the signal is sent to the fuel injection ECU where it is processed to determine the optimal air/fuel ratio to meet the specific demands of
the engine.
The sensor is mounted close to the flywheel (2) which circumference is provided with a series of drilled holes.
CONSTRUCTION (A)
The sensor (1) consists of a permanent magnet (4), a pole tip (5) which concentrates a magnetic field at the end of the device and a coil (6). The
magnet creates a magnetic field which varies in strength depending on whether a hole or "tooth" is passing the tip.
OPERATION
Voltage is induced in the sensor when one of the "teeth" on the flywheel passes the tip. This variable signal is transmitted by wire to the ignition
ECU.
In effect, the sensor supplies the ignition ECU with a unique altering voltage (an electrical picture) from which the ignition ECU can determine
both the crankshaft position and speed.
SIGNAL (B)
The frequency (7) of the signal is used to determine the engine speed.
To provide a referance signal for the crankshaft position, one or more "teeth" on the flywheel circumference are made longer than others. The
ignition ECU detects the crankshaft position by sensing the interruption in the signal (8) which occurs as a long "tooth" passes the sensor. This
referance is used to determine the top dead center (TDC) position.
