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Bad Crank Sensor Symptoms

by Robert Tomashek

Over the years vehicle manufacturers have create engines that are more powerful and efficient, yet with smaller displacement. Technology has helped eliminate systems like point ignition that rely on mechanical movement to fire the ignition coil. Now our engines are computer controlled, with one of the main inputs being the crankshaft position sensor. Just about every engine today has a crank sensor that sends a signal to the computer regarding engine speed. This signal allows the computer to calculate timing and to identify various issues with the engine. Knowing the symptoms of a failing crank sensor will help to diagnose many running issues.

The Check Engine Light

When a crank sensor is in the early stages of failure the vehicle's computer may turn on the "Check Engine" light. You may not have any other symptoms, but this is the vehicle's way of telling you that it sees something that is not right.

Missing Crank Signal

If the crank sensor completely fails, the computer can no longer calculate engine speed. When this occurs, the ignition system and the fuel system shut down causing the engine to crank and not start or to stall if the engine is running.

Intermittent Crank Signal

If the crank sensor sends a signal that is intermittent or shows the wrong crank position it can cause rough idling, backfiring and loss of power.

About the Author

Robert Tomashek is an automobile technician and educator with more than 15 years of experience. He is ASE master certified and also carries certifications from IMACA, MOOG, Monroe, EPA and Four Seasons. He has a degree in automotive/diesel technology. He has written articles for various websites and teaches automotive technology at Universal Technical Institute.

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