Crankshaft Sensor

Crankshaft Sensor:

Crankshaft Balancer With Interrupter Rings:

Crank Sensor Pulses:

DESCRIPTION
The dual crankshaft position sensor, secured in an aluminum mounting bracket and bolted to the front left side of the engine timing chain cover, is partially behind the crankshaft balancer. A 4-wire harness connector plugs into the sensor, connecting it to the electronic ignition module.
The dual crankshaft position sensor contains two Hall-effect switches with one shared magnet mounted between them. The magnet and each Hall-effect switch are separated by an air gap. A Hall-effect switch reacts like a solid-state switch, grounding a low-current signal voltage when a magnetic field is present. When the magnetic field is shielded from the switch by a piece of steel placed in the air gap between the magnet and the switch, the signal voltage is not grounded. If the piece of steel (called an interrupter) is repeatedly moved in and out of the air gap, the signal voltage will appear to go "ON-OFF-ON-OFF-ON-OFF." Compared to a conventional mechanical distributor, this "ON-OFF" signal is similar to the signal that a set of breaker points in the distributor would generate as the distributor shaft turned and the points opened and closed.

OPERATION
In the case of the electronic ignition system, the piece of steel is two concentric interrupter rings mounted to the rear of the crankshaft balancer. Each interrupter ring has blades and windows that, with crankshaft rotation, either block the magnetic field or allow it to reach one of the Hall-effect switches. The outer Hall-effect switch is called the 18X crankshaft position sensor, because the outer interrupter ring has 18 evenly-spaced same-width blades and windows. The 18X crankshaft position sensor produces 18 "ON-OFF" pulses per crankshaft revolution. The Hall-effect switch closest to the crankshaft, the 3X crankshaft position sensor, is so called because the inside interrupter ring has 3 unevenly-spaced, different-width blades and windows. The 3X crankshaft position sensor produces 3 different length "ON-OFF" pulses per crankshaft revolution.

When a 3X interrupter ring "window" is between the magnet and inner switch, the magnetic field will cause the 3X Hall-effect switch to ground the 3X signal voltage supplied from the ignition control module. The 18X interrupter ring and Hall-effect switch react similarly. The electronic ignition module interprets the 18X and 3X "ON-OFF" signals as an indication of crankshaft position, and must have both signals to "fire" the correct ignition coil.

The electronic ignition module determines crankshaft position for correct ignition coil sequencing by counting how many 18X signal transitions occur, i.e.; "ON-OFF" OR "OFF-ON," during a 3X pulse.