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What Causes Crankshaft Sensor to Go Bad?

What Causes Crankshaft Sensor to Go Bad?

A crankshaft sensor is an electronic device used in an internal combustion engine to monitor the crankshaft position and determine its rotating speed in terms of revolutions per minute (RPM).

The crankshaft position sensor (CKP sensor), as it’s known in the full name, is mounted to the timing belt cover of the engine and facing the timing belt’s pulley (rotating teethed wheel).

The crank sensor is electric, so it works on principles of electric and electromagnetic. There is dire need for you to understand what causes crankshaft sensor to go bad hence raise preventive measures.

When the toothed wheel spins together with the crankshaft, the rotating pins disrupt the sensor’s magnetic field, creating an on and off switching pattern.

With this pattern, the crank sensor sends the signals to the Engine Control Unit (ECU), which interprets the speed of the crankshaft in terms of RPM.

Depending on the information the ECU receives from the crankshaft position sensor, it’s able to control two processes;

  • Fuel-oxygen ratio to inject into combustion chamber and timing.
  • Spark ignition timing

What Causes Crankshaft Sensor to Go Bad?

Image: Crankshaft

Although the crankshaft sensor is located in a well-covered area with the timing cover, it can go bad due to the normal wear and tear. However, several reasons cause it to go bad;

  • Overheating engine
  •  Crank Walk
  •  Faulty wiring harness
  • Damaged/worn out timing belt or chain
  • Damaged crankshaft pulley (teethed wheel)
  • Excessive vibration and poor installation
  • Metal shavings on sensor magnet

Related: How to reset camshaft position sensor

1. Overheating Engine

Image: car engine

Excessive heat from the engine causes the plastic casing of the sensor to melt or crack.

As a result, the circuit system inside the casing loosens or detaches from its connection, hindering signal delivery to the ECU.

Secondly, excessive heat hinders the sensor’s magnet monitoring the spinning wheel.

As that’s the case, ensure your car is well lubricated, has no ventilation problems, the radiator and the cooling system pipes aren’t blocked to avoid overheating.

2. Crank Walk

Image: Crankshaft

The Crank Walk is a term used to describe a condition where the crankshaft slides out to the belt’s side. The main cause is mostly a worn-out main thrust bearing.

The metal plate protruding from the crankshaft may strike the sensor, causing damage. If Crank Walk happens, you may notice a clicking noise when the engine runs.

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3. Faulty Wiring Harness

Image: Crankshaft

For the crankshaft position sensor to transmit the signal to the Engine Control Unit, both are connected by a wire harness. Faulty wiring leads to incorrect voltage or no power for the electric and electromagnetic functionality.

Faulty wiring may occur due to;

  • Loose wires detach from their connection.
  • Oil contaminants due to the worn-out main thrust bearing.
  • Damaged/Worn Out Timing Belt or Chain

After a collision, a damaged timing chain may wrap the crankshaft, or a worn-out timing belt may strike the sensor at speed with its fibre strands, damaging the components.

4. Damaged Crankshaft Pulley (Teethed Wheel)

The crank sensor gauges the electromagnetic pulses by monitoring the rotation of crankshaft pulley pins. If some pins are missing or compromised, the pulse pattern becomes inconsistent.

For that reason, the crankshaft sensor may release inaccurate information to the ECU. Secondly, inappropriate patterns may soon tamper with the sensor magnet’s functionality.

5. Excessive Vibrations and Poor Installation

If the engine extremely vibrates or excessive vibration due to a rough road, the internal wiring of the sensor may loosen.

On the other hand, when replacing the crank sensor, ensure all connections are tightened to avoid disconnection.

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6. Metal Shavings on Sensor Magnet

Metal shavings attracted by the sensor magnet act as a bridge between the sensor and the timing belt’s pulley. These shavings hinder monitoring the magnet’s pulley pins movement, causing poor signal.

Metal shavings appear from the surrounding areas of the timing cover due to the engine moving part’s friction.

Image: car engine

What Are Symptoms of Bad Crankshaft Position Sensor?

Although most car manufacturers recommend vehicle scanning to know the exact area that needs repair, some symptoms may signal you if the crankshaft sensor is bad;

  • Difficulty starting the engine
  • Check engine light turns on
  • Stalling engine
  • Rough idling and jerky acceleration
  • Misfiring engine and poor gas mileage
Image: Crankshaft

a) Difficulty Starting the Engine

Difficulty in starting the engine results from poor fuel and ignition timing information released by the Engine Control Unit.

b) Check Engine Light Turns On

Although check engine light illuminates due to several issues with the various engine components, a faulty crankshaft position sensor may be one of them.

But if you combine the check engine light with other discussed symptoms, you may have a clear assurance of crank sensor error in your car.

However, the best action is to scan your car for error codes and know the area that needs repair if the check engine warning appears.

Image: Crankshaft

c) Stalling Engine

At some point, when driving or idling, the engine may stall if the ECU releases inappropriate ignition and fuel injection timing information.

d) Rough Idling and Jerky Acceleration

Rough idling and jerky acceleration are a result of an imbalanced fuel-oxygen ratio. If the RPM is not well monitored, the ECU will not perfectly determine the actual oxygen and fuel ratio to enter the combustion chamber. 

Image: Crankshaft

e) Misfiring Engine and Poor Gas Mileage

If the ignition timing is inappropriate, the fuel injected into the combustion chamber will miss fire. As a result, unburned fuel will be expelled through the tailpipe.

On the other hand, excess fuel will be left unburned if the oxygen-fuel ratio isn’t balanced into the combustion chambers. Afterward, it will be expelled as exhaust gas leading to wastage.  

Can a Bad Crankshaft Sensor Cause Limb Mode?

The ECU is programmed to activate Limb Mode in modern cars immediately when the engine isn’t fully functioning. The action aims at protecting the engine from extreme damages until the faulty part is repaired.

As that’s the case, a crankshaft position sensor error isn’t an exception. The ECU will activate the Limb Mode.

How Long Does a Crankshaft Position Sensor Last?

Since the crank sensor functions every time the engine runs, it can fail due to wear and tear. However, the time it would last depends on your driving habit and routine maintenance practices like;

  • Cleaning the sensor magnet to remove metal shavings
  • Replacing worn-out timing belt or chain.
  • Good engine lubrication
  • Cleaning the car’s cooling system.

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You’ve learned many risk factors that causes crankshaft sensor to go bad despite wear and tear. However, as a car enthusiast, you’ll need to carry out routine maintenance practices for the sensor keenly and stay mobile. 

Read: What are common causes of a vacuum leak?

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