Beretta V6-3100 3.1L VIN M SFI (1995)
Crankshaft Position Sensor: Description and Operation
Crankshaft Position (CKP) Sensor(s)
3X Crankshaft Position Sensor
24X Crankshaft Position Sensor
GENERAL INFORMATION
This engine uses two crankshaft position sensors. One sensor, mounted on the side of the engine block (3X crankshaft sensor), and another (24X
sensor) mounted on the front of the engine behind the harmonic balancer.
The 24X crankshaft position sensor, secured in an aluminum mounting bracket and bolted to the front side of the engine timing chain cover, is
partially behind the crankshaft balancer "On-Vehicle Service."
The 3X crankshaft position sensor uses a two wire connector at the crankshaft position sensor and a three-wire connector at the ignition control
module.
The 24X crankshaft position sensor contains a Hall effect switch. The magnet and Hall-effect switch are separated by all air gap. A Hail-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.
In the case of the electronic ignition system, a concentric Interrupter ring mounted to the rear of the crankshaft balancer has blades and windows
that, with crankshaft rotation, either block the magnetic field or allow it to reach the Hall-effect switch. The Hall-effect switch is called a 24X
crankshaft position sensor, because the interrupter ring has 24 evenly-spaced same-width blades and windows. The 24X crankshaft sensor produces
24 "ON-OFF" pulses per crankshaft revolution. The Hall-effect switch closest to the crankshaft, the 3X crankshaft position sensor, is so called
because the interrupter ring has a special wheel cast on the crankshaft that has seven machined slots, six of which are equally spaced 6O° apart. The
seventh slot is spaced 100 from one of the other slots. As the interrupter ring rotates with the crankshaft, the slots change the magnetic field. This
will cause the 3X Hall-effect switch to ground the 3X signal voltage supplied from the ignition control module. The ignition control module
interprets the 3X "ON-OFF" signals as an indication of crankshaft position, and must have the 3X signal to "fire" the correct ignition coil.
The 24X interrupter ring and Hall-effect switch react similarly. The 24X signal is used for better resolution at a calibrated RPM.
