Crankshaft (3X/7X & 24X) Sensor

The Crankshaft Position (CKP) sensor "A" contains a Hall Effect switch located on the front side of the motor above and forward of the oil filter. See Fig 1 and Fig 2 . A Hall Effect switch is a solid state switching device that produces a digital ON/OFF pulse when a rotating element passes between the sensor tip and a magnet. This rotating element is called an interrupter ring or blade. In this case the interrupter ring has 24 evenly spaced blades and windows and is part of the crankshaft damper assembly. This sensor provides the Powertrain Control Module (PCM) with 24X signals, or 24 identical pulses per crankshaft revolution. The 24X signal is used for enhanced smoothness and idle stability at a lower calibrated RPM. The PCM supplies the sensor with a 12-volt reference, low reference, and signal circuit.

The CKP sensor "B" is a variable reluctance sensor located behind the crankshaft pulley. See Fig 3 . The magnetic field of the sensor is altered by a crankshaft mounted reluctor wheel that has seven machined slots, six of which are equally spaced 60 degrees apart. The seventh slot is spaced 10 degrees after one of the 60 degree slots. This sensor provides the Ignition Control Module (ICM) with 7X signals, or seven pulses for each revolution of the crankshaft. The pulse from the 10 degree slot is known as the sync pulse. Both of the sensor circuits are connected to the ICM. A signal converter within the ICM produces digital 3X output pulse to the PCM, the 3X reference is known as the low resolution engine speed signal.

Fig 1: Locating CKP Sensor "A" Harness Connector & Knock Sensor

Courtesy of GENERAL MOTORS CORP.