Regal V6-3.8L SC VIN 1 (1998)
Crankshaft Position Sensor: Description and Operation
Crankshaft Position Sensor
Crankshaft Position Sensor
The dual crankshaft position sensor is secured in an aluminum mounting bracket and bolted to the front left side of the engine timing chain cover,
partially behind the crankshaft balancer. A 4-wire harness connector plugs into the sensor, connecting it to the ignition control 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.
Balancer Interrupter Rings
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 either block the magnetic field or allow it to close one of the Hall effect switches. The outer Hall effect
switch produces a signal called the CKP 18X because the outer interrupter ring has 18 evenly spaced blades and windows. The CKP 18X portion of
the crankshaft position sensor produces 18 ON - OFF pulses per crankshaft revolution. The Hall-effect switch closest to the crankshaft, the CKP Sync
portion of the sensor, produces a signal that approximates the inside interrupter ring. The inside interrupter ring has 3 unevenly spaced blades and
windows of different widths. The CKP Sync portion of the crankshaft position sensor produces 3 different length ON - OFF pulses per crankshaft
revolution. When a CKP Sync interrupter ring window is between the magnet and inner switch, the magnetic field will cause the CKP Sync Hall effect
switch to ground the CKP Sync signal voltage supplied from the ignition control module. The CKP 18X interrupter ring and Hall-effect switch react
similarly. The ignition control module interprets the CKP 18X and CKP Sync ON - OFF signals as an indication of crankshaft position, and the
ignition control module must have both signals to fire the correct ignition coil. The ignition control module determines crankshaft position for correct
ignition coil sequencing by counting how many CKP 18X signal transitions occur, i.e.; ON - OFF or OFF - ON, during a CKP Sync pulse.
