BODY AS-OIL PUMP 9P7470 - Caterpillar

Crankshaft Position Sensor and Camshaft Position Sensor
The engine utilizes a camshaft position sensor and a crankshaft position sensor.The camshaft sensor is a 2 wire (passive sensor).The crankshaft sensor is a 3 wire (active sensor).The crankshaft sensor detects holes in the flywheel. There a 24 holes drilled radially into the flywheel circumference. The holes are drilled on 10 degree centers. This action results in one wide gap of 20 degrees between two holes.The 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 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 crankshaft position. 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.
Illustration 1 g03719224
Crankshaft sensor and camshaft sensor
Inline engine is shown for this illustration.
(1) Flywheel holes (one 20 deg gap)
(2) Crankshaft sensor (active sensor)
(3) Camshaft sensor (passive sensor)
(4) Extra tooth Crankshaft Sensor Location
The mounting location for the sensor will vary with the type of flywheel that is used.
Illustration 2 g03872602
(1) High Inertia flywheel
(2) Standard flywheel