DISC 1V4540 - Caterpillar

engine speed/timing sensors provide information about engine speed and about the position of the crankshaft to the Electronic Control Module (ECM). The sensors monitor the rotation of a speed/timing wheel. The passive sensors have a coil around a permanent magnet which generates voltage as the teeth of the speed/timing wheel pass through the magnetic field. The speed/timing wheel is installed on the rear of the right camshaft.The engine speed/timing sensor generates a signal that matches the pattern of the speed/timing wheel's teeth. The ECM monitors the speed of the signal pulses in order to determine the engine rpm.The speed/timing wheel has a special tooth pattern that indicates the position of the camshaft. The speed/timing wheel has 36 teeth that are evenly spaced and one extra tooth. The number one cylinder is at the top center position on the compression stroke when the centerline of the first tooth after the extra tooth aligns with the centerline of the sensor. All 37 teeth pass the sensors during one revolution of the camshaft or two revolutions of the crankshaft.With the information from the engine speed/timing sensors, the ECM is able to calculate the positions of the pistons in the cylinders. The ECM determines the desired timing according to the engine speed and to the load. The ECM sends voltage pulses to the fuel injectors according to the desired timing.If the engine speed/timing sensor is replaced, the sensor does not require calibration and the speed/timing wheel does not require adjustment.