Engine RPM detection

Hi and thanks for using 2CarPros. Com.

The truck does not have a traditional crankshaft position sensor. Instead, it has a misfire sensor and pulse ring. This sensor is an electromagnetic inductance coil similar in operation to a camshaft or crankshaft position sensor. A four-point stator, or pulse ring, located behind the crankshaft damper generates an electrical impulse in the sensor at each 90 degrees of rotation. The Powertrain Control Module (PCM) monitors the sensor pulses and flags any misfire events. When a specified number of misfires occur within a certain time frame, the PCM will alert the driver to the condition by turning on the Malfunction Indicator Light (MIL). Via this sensor, a rev-limiter is activated.

I attached a picture of the component. I hope this is helpful.

Take care,
Joe

I looked back to 1995 and the only thing I found that makes any sense is in the distributor. There is a hall effect vane switch assembly, to allow the ignition coil to be switched off and on by the PCM and (ICM). That is the only way I can find that the engine RPM/speed could be calculated. Since this is an early 1996, take a look at the following and compare it to what you have.

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DESCRIPTION AND CONSTRUCTION
The universal distributor has a Hall effect vane switch assembly, to allow the ignition coil to be switched OFF and ON by the Powertrain Control Module (PCM) and Ignition Control Module (ICM).

Vane Switch
The vane switch is an encapsulated package consisting of a Hall effect device on one side and a permanent magnet on the other side.

OPERATION

Rotary Vane Cup
A distributor armature, made of ferrous metal, is used to trigger the signal OFF and ON.

Magnetic Flux Field

When the window of the distributor armature is between the magnet and the Hall effect device, a magnetic flux field is completed from the magnet through the Hall effect device and back to the magnet.
As the vane passes through this opening, the flux lines are shunted through the vane and back to the magnet. During this time, a voltage is produced as the vane passes through the opening. When the vane clears the opening, the window edge causes the signal to go to zero volts. This signal is used by the PCM for crankshaft position sensing and the computation of the desired spark advance based on engine demand and calibration. The conditioned spark advance and voltage distribution is done with a conventional distributor rotor, distributor cap, and distributor to spark plug wires.

Your thoughts?