Engine Speed Sensor/Crankshaft Position Sensor (Cps)
The engine speed sensor (CPS) is attached to the flywheel housing and is not adjustable. See Fig 1 . The CPS is a speed sensor that provides an input signal to the ECU relating to crankshaft angle position. The ECU converts the rate of crankshaft angle into engine RPM and crankshaft angle to piston position.
The flywheel has 3 trigger notches located 120 degrees apart. There are 20 small teeth between each trigger notch. Each large trigger notch is located 12 small teeth before each Top Dead Center (TDC) position of each corresponding piston. When a tooth or notch pass the magnet core of the speed sensor, a voltage spike is induced in the sensor pick-up coil winding. These voltage spikes allow the ECU to count the teeth as they pass the sensor. When a trigger notch passes the speed sensor, there is a longer than usual delay between voltage spikes. This longer delay tells the ECU that a piston will be at the TDC position 12 spikes later. The ECU also uses information from the speed sensor to control spark timing and fuel injection timing for each cylinder.