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Faulty Crankshaft Position Sensor (Signs & Symptoms)

Updated: Jan 9

The crankshaft position sensor is a crucial element of a modern internal combustion engine. It's function is to keep track of the position and speed of the crankshaft.


A faulty crankshaft position sensor will typically show a number of signs and symptoms, such as the following.


  • Illumination of the check engine light (CEL)

  • Reduced engine performance

  • Worsened fuel efficiency

  • Difficulty starting the engine

  • Rough idle and increased vibrations

  • Shuddering, shaking and jerking

  • Stalling

  • Misfiring


If you scan the ECU with an OBD scanner you may also notice a P0335 diagnostic fault code.

 

Table of Contents:


diagram of how a crankshaft position sensor works
Diagram of How a Crankshaft Position Sensor Works

What Is the Crankshaft Position Sensor?

This sensor will provide data to the engine control unit (ECU), which will use it to control the ignition and fuel injection timing. When paired with the camshaft position sensor, the crankshaft position sensor allows the engine to be perfectly in sync.


A crankshaft position sensor is often located around the flywheel or at the primary crank pulley in the engine bay's bottom.


If this sensor fails it will cause the engine to go out of sync, the ECU will be unable to correctly set ignition and fuel injection timing and the engine will run very poorly or may not run at all.


Sometimes the issue is intermittent and the sensor will work fine one minute and the next minute it will fail.


Signs & Symptoms of a Faulty Crankshaft Position Sensor

The most obvious sign of a malfunctioning crankshaft position sensor is the illumination of the check engine light. Although a check engine light is a common symptom of this sensor malfunctioning, it can be caused by many other reasons.


The most common OBD fault code related to the crankshaft position sensor is a P0335 code.


Reduced Engine Performance

In the event that the crankshaft position sensor of an engine fails, it may not move into higher RPMs as easily or at all, and if it does, it may result in engine knocking and detonation.


Knocking and detonation of the air/fuel mixture within the engine can be caused by spark plug ignition at the wrong time, causing very high pressure and shockwaves inside the combustion chamber, potentially leading to serious engine damage.


You will likely notice higher fuel consumption, less power, and slower acceleration.


Worsened Fuel Efficiency

Incorrect fuel injection and ignition timing causes a reduction in fuel efficiency, as a result you'll likely notice a worsened fuel economy as a result of a crankshaft position sensor failing.


car fuel gauge reading empty

Difficulty Starting the Engine

Starting problems are another common sign of a faulty or malfunctioning crankshaft position sensor. The sensor provides the ECU data that is crucial for starting the engine.


The vehicle may start intermittently or may not start at all if the crankshaft position sensor isn't working properly. Keep in mind this can cause a breakdown situation if left unfixed.


Note that there are some tips you can try to help start a car with a bad crankshaft sensor but they're only temporary fixes and not a permanent solution.


person putting car key in car ignition

Rough Idle and Increased Vibrations

A rough idle is another indication of a crankshaft position sensor issue.


You may hear and feel the engine vibrating when idling. The sensor is crucial in keeping the engine running smoothly and in sync.


Shuddering, Shaking and Jerking

An engine vibrating is a more minor effect, if it gets worse it can result in shuddering, shaking and jerking. The engine has been tuned to run smoothly with very little vibration. When the crankshaft position sensor malfunctions, the engine will lose sync and shudder, shake, and jerk.


If the engine is left running in this manner, it may suffer severe damage. It can also cause the transmission and engine mounts to rupture.


Stalling

Intermittent stalling is a symptom often associated with a crankshaft position sensor issue. Stalling may be a common issue or infrequent depending on the vehicle and how severe the issue is.


When accelerating or under heavy loads like climbing a steep hill or accelerating from a standstill, you might notice the engine has less power and stalls.