Crankshaft position sensor (345), Simtec: Connection

The sensor works as a generator and provides a sine form alternating current. By measuring the frequency the control module can determine the engine speed. After the perforated disc's 58th rib there are two ribs missing. When rib 1 then passes the sensor the control module knows that the crankshaft is 114 before top dead center (TDC). If the crankshaft position sensor does not work then the signal from the camshaft sensor is used as a substitute value, although with inferior engine performance.

Voltage from the crankshaft sensor varies with engine speed. It is the frequency, not voltage, that is important to the control module. As soon as the control module receives pulses from the crankshaft sensor, it grounds the fuel pump relay.

Fig 1: Circuit Diagram Crankshaft Position Sensor (345) Simtec

Courtesy of SAAB-SCANIA OF AMERICA, INC.