Crankshaft Position Sensor

The Crankshaft Position (CKP) sensor is located in the front cover of the cylinder block near the crankshaft pulley. CKP sensor is a magnetic generator type sensor, producing an alternating current signal. The CKP sensor signal increases in both frequency and amplitude as the engine RPM increases. The CKP sensor sends this reference signal to the Powertrain Control Module (PCM) to indicate the crankshaft RPM and position. This reference signal is used by the PCM to calculate fuel injection pulse, establish Top Dead Center (TDC) for ignition timing and where to start ignition coil and injection sequencing. There will be no spark or fuel delivery if there is no CKP sensor signal. The PCM uses the CKP sensor signal along with the camshaft position (CMP) sensor signal for the following purposes:

• To calculate the fuel injector pulse.
• To establish the piston position TDC for the ignition timing.
• To start the ignition coil and fuel injection sequencing.

The CKP sensor reluctor has 34 teeth and is mounted on the crankshaft behind the timing chain cover and the crankshaft pulley. See Fig 1 . When the crankshaft rotates, the CKP sensor signal rotor teeth pass by the CKP sensor causing a fluctuation in the sensors magnetic field. The fluctuation in the magnetic field induces a voltage in the CKP sensor circuitry that corresponds to every 10 degrees of crankshaft rotation. The reluctor has one wide tooth that indicates TDC of the number 1 cylinder. With the information that the PCM receives from the CKP sensor, the PCM determines engine speed and crankshaft position.

Fig 1: Identifying Crankshaft Position Sensor Components

Courtesy of GENERAL MOTORS CORP.