Engine Speed Sensor (Crankshaft Position Sensor - Cps)
The engine speed sensor is attached to the flywheel cover housing and provides an input signal to the ECU relating to crankshaft speed, angle, and position. See Fig 1 . The ECU converts crankshaft speed input into engine RPM and converts crankshaft angle to piston position. The engine speed sensor senses TDC, BDC, and engine speed by detecting the flywheel teeth as they pass by the sensor during engine operation. The engine speed sensor is non-adjustable.
The flywheel has three trigger notches, 120° apart. See Fig 1 . 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 the corresponding pistons.
When a small tooth and notch pass the magnet core in the sensor, the concentration, followed by the collapse of the magnetic flux induces a small voltage spike to the sensor pickup coil winding. These small voltage spikes enable the ECU to count the teeth as they pass the sensor. When a large trigger tooth and notch pass the magnetic core in the sensor, the increased concentration, and then collapse of the magnetic flux induces a higher voltage spike into the sensor pickup coil winding. See Fig 2 .
The higher voltage spike is an indication to the ECU that a piston will reach its TDC position, 12 teeth later. See Fig 3 . The ignition timing for the particular cylinder is either advanced or retarded as necessary by the ECU according to sensor inputs.