GM Cadillac Deville_Fleetwood_ELD_Seville 1990-1998

Crankshaft Position Sensor


For procedures on the position sensors, please refer to electronic engine controls.

The 2 crankshaft sensors are located on the front of the engine block, between cylinder Numbers 4 and 6. Crankshaft position A sensor is located on the upper crankcase and crankshaft position B sensor is located in the lower crankcase. Both sensors extend into the crankcase and are sealed into the engine block with O-rings. The crankshaft position sensors are not adjustable.

The magnetic crankshaft position sensors operate similar to the pick-up coil in a distributor. When a piece of steel, called the reluctor, is repeatedly moved over the sensor, a voltage will be created that appears to go ON-OFF-ON-OFF-ON-OFF. This ON-OFF signal is also the signal that a set of breaker points in a distributor would generate as the distributor shaft turned and the points open and closed.

Reluctor Ring

The reluctor ring is cast onto the crankshaft between the No. 3 and No. 4 main bearing journals. The reluctor ring has 24 evenly spaced notches or air gaps and additional 8 unevenly spaced notches for 32 notches. As the crankshaft makes one revolution, both A and B sensors will produce 32 ON-OFF pulses per revolution. In addition, the "A" sensor is positioned 27 degrees of crankshaft revolution before the B sensor. This creates a unique pattern of ON-OFF pulses sent to the ignition control module so that it can recognize crankshaft position.