9-3 Convertible (9400) L4-2.0L Turbo (2.0 HOT) (2003)
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Crankshaft Position Sensor: Description and Operation
Crankshaft Position Sensor
The control module receives information on the position and speed of the crankshaft on pins 17 and 18 from the crankshaft position sensor.
There is a slotted ring with 58 ribs on the crankshaft. The sensor is of the inductive type and is fitted to the wall of the engine crankcase. The distance
between the sensor and the slotted ring is between 0.4 - 1.3 mm and is not adjustable.
The sensor acts like a generator and delivers a sinusoidal alternating current. By measuring the frequency, the control module can determine the engine
speed. There are two ribs missing after the 58th one. When rib 1 subsequently passes the sensor, the control module will know that the crankshaft is 117
before top dead centre (BTDC).
The voltage from the crankshaft position sensor varies with the engine speed. At idling speed, the voltage is 5 - 10 V (AC) and at 2500 rpm, approx. 15
- 20 V (AC). However, it is the frequency and not the voltage that is of interest for the control module.
As soon as the control module receives pulses from the crankshaft position sensor, it will ground the fuel pump relay.
The resistance of the sensor is 860 ±90 ohms.
