Engine Speed Sensor: Description and Operation

CRANKSHAFT POSITION SENSOR (CKP)-ECM INPUT

Crankshaft Position Sensor (CKP) Location:

The Crankshaft Position Sensor (CKP) is located on the lower left-rear side of the engine behind the starter motor.

Engine speed and crankshaft position are provided through the CKP. The sensor generates pulses that are the input sent to the Engine Control Module (ECM). The ECM interprets the sensor input to determine the crankshaft position. The ECM then uses this position, along with other inputs, to determine injector firing sequence and fuel timing. The sensor must be powered up by 5 volts to operate.

The sensor is a hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.

Crankshaft Tone Wheel:

The engine crankshaft is equipped with a bolt-on tone wheel. The tone wheel is equipped with 35 teeth and a gap where the 36th tooth should be placed. This missing tooth indicates to the ECM the relative position of cylinder #1 to the Top Dead Center (TDC) position. This does not mean that cylinder #1 is at TDC. When the CKP is aligned with the missing tooth, the missing tooth is 60 degrees away from cylinder #1 TDC position. The teeth cause pulses to be generated when they pass under the sensor. The pulses are the input to the ECM.