What Are the Top 7 Signs of a Faulty Crankshaft Position Sensor?

Recognize the top 7 signs of a faulty Crankshaft Position Sensor and troubleshoot the problem effectively.
What Are the Top 7 Signs of a Faulty Crankshaft Position Sensor?
Key Points
The crankshaft position sensor (CPS) measures the rotational speed and position of the crankshaft in a vehicle’s engine.
Symptoms of a faulty CPS include issues starting the vehicle, intermittent stalling, and illuminated check engine light.
Additional symptoms may include poor acceleration, misfires, backfiring, or unusual engine sounds.
A faulty CPS can cause mismatched fuel delivery and ignition timing, leading to drivability issues and reduced performance.
Testing the CPS involves using a multimeter to check resistance or voltage readings, and comparing them to manufacturer specifications.
Replacement CPS should be compatible with the vehicle make and model, and properly calibrated to ensure accurate readings.
Regular maintenance and care of a vehicle can help prevent CPS failure due to grime, oil, water damage, bad wiring, or overheating.
Addressing CPS issues promptly can help prevent further damage to other engine components, and maintain overall vehicle performance.

The crankshaft position sensor is an integral part of a vehicle’s engine management system. It monitors the speed and position of the crankshaft, which is vital information for controlling the fuel injection process and ignition timing. If the crankshaft position sensor starts to fail, your vehicle may exhibit various symptoms. Here are the top seven signs that your crankshaft position sensor may be faulty.

1. Check Engine Light

The most common sign of a faulty crankshaft position sensor is when the check engine light illuminates on your dashboard. This warning light can be triggered by a variety of issues, including a failing crankshaft sensor. However, this usually requires a diagnostic tool to confirm, as the check engine light alone is not definitive.

2. Intermittent Stalling

If your vehicle stalls unexpectedly during operation, especially at low speeds or while at a stop, it could indicate a problem with the crankshaft position sensor. A malfunctioning sensor can send incorrect signals to the vehicle’s computer, causing the engine to stall.

3. Irregular RPM Readings

The revolutions per minute (RPM) of your engine can be inconsistent if your crankshaft position sensor is failing. You might notice the tachometer jumping erratically or the engine running unevenly, which can signal an issue with the sensor.

4. Difficulty Starting the Vehicle

A faulty crankshaft position sensor can cause difficulties when starting the vehicle. As the sensor controls the ignition timing and fuel injection, if it isn’t working correctly, the vehicle may struggle to start or may not start at all.

5. Poor Engine Performance

A malfunctioning crankshaft position sensor can lead to poor engine performance, with symptoms such as reduced power, lower fuel efficiency, or acceleration issues. These problems can arise due to incorrect information being relayed to the vehicle’s computer about the crankshaft’s speed and position.

6. Engine Vibration or Misfire

A faulty sensor can disrupt the engine’s balance, leading to noticeable vibrations while the vehicle is in motion or idle. The engine may also misfire due to incorrect ignition timing or fuel injection, which is another symptom of a faulty crankshaft position sensor.

7. Failed Emissions Test

A vehicle with a faulty crankshaft position sensor may fail an emissions test due to an incorrect air-fuel mixture or incorrect ignition timing. This can lead to higher emission levels, causing the vehicle to fail the test.


A faulty crankshaft position sensor can lead to several problems that affect your vehicle’s performance and fuel efficiency. If you notice any of the above signs, it’s advisable to have your vehicle checked by a professional mechanic promptly. Remember, these symptoms are common to many vehicle problems, so a thorough diagnosis is necessary to avoid unnecessary repairs.

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What is a crankshaft position sensor and what is its role?

The crankshaft position sensor is a component in modern vehicles that monitors the position or rotational speed of the crankshaft. This information is used by engine management systems to control the fuel injection and ignition timing, contributing to the engine’s overall performance and efficiency.

What are the common signs of a faulty crankshaft position sensor?

Common signs of a faulty crankshaft position sensor include issues like difficulty starting the car, intermittent stalling, irregular idle, the ‘Check Engine’ light coming on, reduced fuel economy, engine misfires, and jerking or surging while driving.

How does a faulty crankshaft position sensor affect the vehicle’s performance?

A faulty crankshaft position sensor can severely affect the performance of the vehicle. As the sensor helps control vital engine functions such as fuel injection and ignition timing, a malfunction can lead to misfires, poor fuel economy, difficulty starting, stalling, and jerking or surging during driving.

Can a car run with a bad crankshaft position sensor?

A car may still run with a bad crankshaft position sensor, but its performance will be significantly compromised and it could even be unsafe to drive. In some cases, the engine might not start or might stall unexpectedly, which can be particularly dangerous while driving.

How is a faulty crankshaft position sensor diagnosed and replaced?

Diagnosing a faulty crankshaft position sensor is typically done by a professional mechanic using an OBD-II scanner to check for related trouble codes. The mechanic might also conduct a visual inspection for signs of damage. If the sensor is deemed faulty, it can be replaced, a process that typically involves disconnecting the negative battery cable, removing the sensor, installing the new sensor, and reconnecting the battery cable.