Differences Between a Camshaft Sensor & a Crankshaft Sensor

by Micah McDunnigan
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The internal-combustion engines that power cars might be strong enough to withstand millions of little explosions over hours of time, but they have delicate timing mechanisms. With precision timing, an internal-combustion engine's combustion chambers are opened, fuel is deposited, chambers are sealed, the fuel is ignited, the explosion forces down a piston (which turns the crankshaft to propel the engine), the chamber is opened again for the smoke to release and more fuel to be deposited. The camshaft and the crankshaft, and their respective sensors, are essential for the engine to keep the correct timing and run properly.


The camshaft sensor monitors the frequency at which the camshaft is turning. The camshaft is a rod with specifically placed protuberances that stick out from the rod. These are called cams. When the camshaft turns, the individual cams push against specific valves and cause them to open. When the cam rotates away from the valve, the valve closes. The camshaft sensor records the rate at which the camshaft is rotating. By extension, this tells the computer the rate at which the engine's valves are opening and closing.


As the gas and air that the valves have pumped into the ignition chambers combust, the force against the piston causes the crankshaft to turn. This turning of the crankshaft is what powers the engine and makes the car move. The crankshaft sensor keeps track of the rate at which the crankshaft is rotating.


The engine computer takes the data from both the crankshaft sensor and the camshaft sensor to evaluate how the engine is performing. Since the camshaft regulates the opening and closing of the combustion chambers through the valves it manipulates, the rotation of the crankshaft is reflective of the rate at which the pistons are firing. Consequently, for the engine to operate properly, the rates of the crankshaft and the camshaft need to be in sync with each other. If the rates begin to differ, the "check engine" light in your car will come on.

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