What Does a Camshaft Interrupter Module Do?

Camshaft position sensors, also known as camshaft position modules, come in several different types. One of the oldest is the magnetic Hall Effect sensor, which utilizes an interrupter gear to determine the crankshaft and camshaft's position.

Magnetic Induction Sensors

Passing a metal through a magnetic field transfers some of the magnet's force to the metal, creating electricity. A Hall Effect sensor uses a gear-like wheel passing in front of a magnet to create a rapid on/off electrical signal that tells the computer where the crankshaft and camshaft are in their rotation.

Comparison

An interrupter-type sensor functions well in most cases, but forces the computer to "guess" where the crankshaft is in the on-to-off signal transition. A second type of sensor uses a reluctor ring with a wavy surface. Instead of an on/off signal, this wavy ring causes the sensor's output voltage to gradually rise and then suddenly fall off. This action gives the computer constant input so it can keep adjusting the fuel injector and ignition timing.

Failure

No permanent magnet is truly permanent, especially when it's been forced to induce current for years on end. Over time the magnet weakens, reducing the sensor's voltage output and sending a false or unsteady signal to the computer. This weakening can result in cylinder misfires, loss of power and an unsteady idle.

References

• AA1 Car Library: Crankshaft & Camshaft Position Sensors
• Free Auto Mechanic: Camshaft Position Sensor (CMP)