Grand Prix V6-191 3.1L VIN M SFI (1998)
Crankshaft Position Sensor: Description and Operation
24X and 7X (CKP) Sensor/Harmonic Balancer Interrupter Ring
DESCRIPTION
The 24X crankshaft position sensor (1), secured in an aluminum mounting bracket (3) and bolted to the front side of the engine timing chain cover (2),
is partially behind the crankshaft balancer (refer to the 24X Crankshaft Position Sensor graphic).
7X Crankshaft Position (CKP) Sensor
The 7X crankshaft position sensor uses a two wire connector at the sensor and a three-way connector at the ignition control module.
24X Crankshaft Position (CKP) Sensor
Description
The 24X crankshaft position sensor contains a Hall-effect switch. The magnet and Hall-effect switch are separated by an air gap.
Operation
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.
Harmonic Balancer Interrupter Ring
Description
In the case of the electronic ignition system, the piece of steel is a concentric interrupter ring mounted to the rear of the crankshaft balancer. The
interrupter ring has blades and windows that, with crankshaft rotation, either block the magnetic field or allow it to reach the Hall-effect switch.
The Halleffect switch is called a 24X crankshaft position sensor, because the interrupter ring has 24 evenly spaced blades and windows. The 24X
crankshaft position sensor produces 24 on-off pulses per crankshaft revolution.
Operation
The 7X crankshaft position sensor is the other Halleffect switch closer to the crankshaft. The interrupter ring is a special wheel cast on the
crankshaft that has seven machined slots, six of which are equally spaced 60 degrees apart. The seventh slot is spaced 10 degrees from one of the
other slots. as the interrupter ring rotates with the crankshaft, the slots change the magnetic field. this will cause the 7X the Halleffect switch to
ground the 3X signal voltage that is supplied by the ignition control module. The ignition control module interprets the 7X on-off signals as an
indication of crankshaft position. The ignition control module must have the 7X signal to fire the correct ignition coil.
