The crankshaft position sensor plays an important role in your car’s engine by monitoring the position of the crankshaft and the speed at which it is rotating. The sensor then transmits this data to the vehicle’s computer to help control fuel injection and ignition timing.
But if it were to fail, you might experience problems starting your car, stalling, or poor engine performance. Understanding the signs of a failing crankshaft position sensor can be the difference between a simple replacement and becoming stranded at the worst possible time.
Common Signs of Bad Crankshaft Position Sensor
A failing crankshaft position sensor often creates noticeable changes in how your vehicle runs. While a single symptom might not confirm a bad sensor, experiencing several of these signs together suggests this component needs attention.
1) Check Engine Light
The most common indicator of a crankshaft position sensor problem is an illuminated check engine light. This happens because your car’s computer constantly monitors the sensor’s signals, and when it detects irregular or missing data, it triggers this warning light.
The most frequent trouble codes associated with this issue are P0335 (Crankshaft Position Sensor Circuit Malfunction) and P0340 (Camshaft Position Sensor Circuit Malfunction). While a check engine light by itself doesn’t guarantee a bad sensor, finding one of these codes along with other symptoms make it very likely.
If you have a code reader, checking for these specific codes can help confirm the issue before visiting a mechanic. If you don’t have access to one, many local auto parts stores will offer free diagnostic scans.
2) Difficult Starting
It’s fairly common to notice problems starting your vehicle if the crankshaft position sensor is on its way out. Since the engine needs to know the exact position of the crankshaft to start properly, a faulty sensor makes this process difficult or even impossible.
The engine may crank longer than usual before starting, or it may take multiple attempts to get the engine running. Cold weather only makes the problem worse since engine components are already under more stress. In severe cases, the engine won’t start at all, even though the starter motor is working correctly and the battery is fully charged.
3) Stalling
An engine that stalls while driving is both frustrating and dangerous and it’s a very possible scenario when your crankshaft position sensor malfunctions. This happens because the sensor periodically fails to send accurate position data to your car’s computer, causing it to lose track of proper fuel injection and spark timing.
You may experience stalling when stopping at a light, slowing down, or even while cruising at highway speeds. Some drivers report their engines stalling more frequently when the engine is warm or during specific weather conditions.
The stalling might happen suddenly without any warning, or you may notice the engine stumbling or running rough just before it dies. This symptom is particularly serious since it may put you in an unsafe situation if the engine cuts out in traffic or leave you stranded in a bad area at a bad time.
4) Hesitation When Accelerating
If your crankshaft position sensor is failing, there’s a good chance you’ll notice a delay or hesitation when stepping on the gas pedal. Again, because your car’s computer needs precise crankshaft position data to determine the correct timing for fuel injection and spark in each cylinder, the computer may briefly hesitate before making these adjustments, creating a noticeable lag in throttle response.
It may feel like your car is “thinking” before responding to your input, or notice a momentary dead spot when trying to accelerate. This hesitation is often more noticeable during quick acceleration, such as when passing another vehicle or merging onto a highway. Suffice to say, it can put you in a dangerous situation if you need to quickly accelerate for whatever reason.
5) Poor Fuel Economy
A bad crankshaft position sensor can significantly impact the amount of miles you get per gallon of fuel. When the sensor sends incorrect signals, your car’s computer might compensate by needlessly injecting too much fuel into the engine (running rich).
You might notice that you’re having to stop for gas more often, even though your driving habits haven’t changed. A 10-20% decrease in fuel economy isn’t unusual when dealing with this issue. Keeping track of your mileage between fill-ups can help identify this symptom early.
While poor fuel economy can have many causes, when combined with other symptoms on this list, it’s a strong indicator you’re dealing with a bad crankshaft position sensor.
6) Engine Misfires
Engine misfires occur when the fuel in your cylinders doesn’t ignite at precisely the right moment, and a failing crankshaft position sensor is sometimes the cause of them. A misfire can feel like as a stumble, hesitation, or jerking sensation, particularly during acceleration but it’s possible to not feel them at all. In some cases, the engine might also feel rough or shake noticeably.
Modern vehicles will often record misfire events in their diagnostic system, which a mechanic can access to help pinpoint the problem. They are typically cylinder-specific so don’t be surprised to see multiple trouble codes stored.
7) Rough Idle
When stopped at a light or sitting in your garage or driveway while warming up, a bad crankshaft position sensor can cause the engine to idle roughly. Instead of a smooth, steady idle where the engine quietly maintains a consistent speed, you’ll notice irregular RPM fluctuations or vibrations coming through the steering wheel and seat.
The tachometer needle might bounce up and down rather than holding steady, and you might hear the engine speed changing. This rough idle may come and go, but it typically becomes more frequent and noticeable as the sensor continues to deteriorate.
Like some of the other symptoms here, rough idling can have multiple causes, but when combined with other symptoms, it often means you’re dealing with a crankshaft position sensor issue.
Crankshaft Position Sensor Replacement Cost
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When it comes time to replace your crankshaft position sensor, expect for it to cost you somewhere between $120 and $260.
The part costs will only be around $40 to $120 depending on the vehicle and whether the new sensor is OEM or aftermarket. The labor cost will be around $80 to $140 as it’s usually fairly easy to reach although sometimes other parts need to be removed to get to it.
Other than the make and model of your vehicle, the total replacement job cost depends heavily on who does the job. Your best bet would be to research a couple independent auto repair shops and get quotes on the cost of replacement. While your local dealership would be happy to replace a simply part like a sensor, expect to pay a premium.
Potential Causes of Failure
A crankshaft position sensor typically lasts between 60,000 to 100,000 miles under normal conditions. However, various factors can cause premature failure or damage to the sensor.
- Excessive Heat Exposure – Constant exposure to high engine temperatures can damage the sensor’s internal components and wiring.
- Wiring Issues – Frayed, damaged, or corroded wires in the sensor’s circuit can interrupt signals or cause complete failure.
- Oil or Fluid Contamination – Oil leaks from worn seals can damage the sensor by coating it in oil or contaminating its electrical connections.
- Vibration Damage – Excessive engine vibration due to bad motor mounts can physically damage the sensor over time.
- Metal Debris – Metal particles from normal engine wear can stick to the magnetic sensor tip, causing inaccurate readings.
- Water Damage – Failed seals or flooding can allow water to enter the sensor housing, causing electrical shorts.
- Physical Impact – Rocks, road debris, or damage during maintenance can crack or break the sensor.
- Age-Related Wear – Electronic components naturally degrade over time, especially in harsh engine environments.
How a Crankshaft Position Sensor Works
Your engine’s crankshaft position sensor is a small device that performs two essential monitoring tasks: tracking the position of the crankshaft and measuring how fast it’s rotating. This data is continuously sent to your car’s computer (ECU).
The sensor’s location near the crankshaft allows it to detect metal trigger points as the crankshaft spins. Using this information, your car’s computer precisely controls the timing of fuel injection and spark for each cylinder. This precise timing is necessary because fuel must be injected and ignited at exactly the right moment for your engine to run properly.
If the sensor fails or sends incorrect data, your car’s computer can’t maintain the correct timing. This leads to various running problems, including the symptoms above.
See Also: Symptoms of a Bad Mass Air Flow Sensor
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