Crankshaft Position Sensor: Description and Operation

Crankshaft Position Sensor:

The Crankshaft Position Sensor (CPS); sometimes called the speed sensor, provides the Electronic Control Unit (ECU) with crankshaft position information. Mounted on the torque converter drive plate housing, the CPS senses Top Dead Center (TDC) and Bottom Dead Center (BDC) by detecting the flywheel teeth as they pass the sensor during engine operation. The CPS also provides the ECU with engine speed information. The drive plate pulse ring has three trigger notches 120° apart and there are 20 small teeth between each trigger notch. Each trigger notch is located 12 small teeth before TDC position of the corresponding cylinder. 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 small notches later. The ECU uses this information along with information from other sensors to control ignition timing.