Should I Replace the Crankshaft Position Sensor?
CARS.COM — Most car owners probably don’t know that their vehicle has a crankshaft position sensor until the engine dies, won’t start or starts running poorly. Then when the car is in the auto repair shop, they find out they need a new one. If ever there was inconvenient timing for your vehicle to signal that you need a repair or replacement, that would be it.
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The crankshaft position sensor, typically mounted near or on the crankshaft, tells the engine computer how fast the engine is running. That’s so the control unit knows when the spark plugs should ignite the air-fuel mixture and, in some engines, when to inject fuel. These sensors are used on virtually all engines that have distributorless ignition systems.
If the crank sensor fails, the computer won’t know how to set the ignition timing, so the engine may stop running or refuse to start. Engine stalling is also a symptom, which can possibly trigger the check-engine light. The engine may run poorly or acceleration may be affected, as well. Excessive heat is a frequent reason these sensors fail, and they also can stop working because of faulty electrical connections or wiring.
Some vehicles also have a camshaft position sensor that allows the engine computer to monitor the position of the camshafts (or camshaft), which open and close the valves, for more precise fuel and ignition management.
These sensors are not listed as routine maintenance items, but they often fail without warning. For that reason, some repair shops recommend they be replaced on high-mileage engines as preventive medicine. Cost can vary depending on the shop, the engine and the age of the car in question.
Since a bad sensor doesn’t always trigger the check-engine light — and some of the same symptoms could be caused by other problems in the fuel or ignition systems — sensors should be tested with a diagnostic scanner or multimeter before deciding to replace them. This is something a mechanic at a reputable repair shop would do before performing the work to repair or replace the sensor.
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