Car Knock Sensor │ What is faulty Knock Sensor?

                 Car Knock Sensor                       

If you want to know and understand the Knock sensor give your ten minutes to this page. And I will try to help you understand everything about it.


We are going to learn about sensor working, importance, location, the position with little about brands. And try to understand why we required it one first place and what could be without this sensor on the engine.

 Table of Contents

  • Working of Knock Sensor
 2.Material & Design 3.Location or Position 4.Faulty Sensor Effect on Engine
  • Be a  Mechanics
 5.Brands 6.Conclusion


Knocking is a phenomenon that occurs inside an engine cylinder during the combustion cycle when high-pressure shock wave change crated by abnormal combustion. In a normal combustion process, Fuel-Air burns and creates high-pressure gas which drives or pushes piston from TDC to BDC and produces work. During the same period a pre-combustion or ignition delay or abnormal combustion of unburnt fuel creates exploded rapidly and collide with existing flame front result in high-pressure shock wave inside cylinder generate a pining sound due to contact made b/w movable parts like piston touching cylinder wall.

➤SI Engine (Spark Ignition) 

Knocking occur in SI engine as soon as spark plug crate spark & unburnt fuel pre-ignite just before the actual combustion separately crate new flame front to pass their heat energy to Fuel-Air mixture through radiation which starts combustion process few milliseconds before its scheduled time and add extra pressure and heat on piston assembly and piston start side motion which creates unwanted sound.

➤ CI Engine (Compression Ignition )

Knocking inside and CI engine occurs due to ignition delay (physical or chemical). After a delay in the ignition by compression large amount of un-burnt mixture of fuel accumulated inside the cylinder as soon as its reaches to high-temperature fuel droplets burst & create high-pressure shock results in pinning sound of the piston assembly.

Other Factor to Knocking

1. The Temperature of Cylinder walls

2. Lean Air-Fuel mixture combustion process

3. Faulty Temperature sensor

4.Fuel injection process 

5.Faulty Spark Plug

6.ECU Fault

⇒Working of Knock Sensor

To prevent knocking or measure its extent engineer comes with a sensor called Knock sensor a very simple design ''Knock Sensor measure or sense vibration coming out inside cylinder to outer surface on engine block'' with the help of physical connection via a nut and bolt with sensor head. As soon as vibration crosses above limits sets during the test to maintain high performance, the efficiency of engine Knock sensor create pulse based on vibration and send it the brain of a vehicle called ECU(Engine Control Unit) based on limit ECU change or adjust course of Fuel injection spark timing to limit knocking.

Design , Material & Function ⇉

Knock Sensor by image by FAE

Upper Body 

Made of plastic having properties to stand high Temperature shock as engine block temperature higher than environment and there is continuous vibration in or out of limit.To resist all these parameters plastic or upper body also need to be corrosion resistance 

Piezoelectric Element

Piezoelectric is the main component of sensor '' it concert vibration into an electrical pulse that measure or scale by processing raw data into readable format '' with the help of ECU. Based on reading ECU identifies what would need to be controlled to limit Knocking.

Seismic Mass

Transfer vibration from the washer to piezoelectric elements this acts as protecting unit to PEE.

Other Parts

⇨Resistance⤍ Provide safety to PE elements.⇨Contact Plate⤍connected with Piezoelectric elements transfers the pulse or signal from elements to wire connected to ECU. ⇨Insulator⤍Protect Piezoelectric elements (PE)from any short circuit from seismic mass and body of the sensor.  ⇨Nut & Washer⤍Nut allows a rigid connection and washer transmit vibration to Seismic Mass.

Location & Position of Sensor

Knock sensors allow us to measure the vibration of the engine so we need a location where vibration is most frequent.

⇒Near Intake Manifold

⇒The upper side of the Engine block

⇒Near Heads of Cylinder

This three-position is very common to mount the sensor with effective measurement.

Location of Knock Sensor

Faulty Sensor Effect on Engine

A faulty or damaged knock sensor could result in less efficiency, the low performance of the car engine. A car with a faulty knock sensor could result.

➠Slow Acceleration

➠High Jerk

➠Low Mileage

➠Engine Check Light  

➠Loss of Engine Power & Efficiency 

➠ A high and long duration of knocking cause damage of Piston, cylinder
This costs a lot to replace so before any things happen to these components go-to the service center.

Be a Mechanic➦  

Whenever we got troubled with our vehicle we will-called or go to the service center. During the time of service at the center if you are their mechanic will perform the following things.Connect Diagnostic Tool provided by OEMs to service center and start reading DTC code this helps the mechanic to identify the problem easily.If not he start rendering to each sensor and check each one by them based on his expertise.As for as Knock sensor is concerned check following⧭  
⇒Check wiring harness connected to Knock Sensor
⇒Check for damaged of sensor
⇒Reconnect wiring harness and check once again if the acceleration of engine normal and no DTC on monitor go drive to future.

Brands or Manufacturer of Knock Sensor

A market is full of different knock sensors based on requirements, specifications, brands as well.When we are talking about requirements mean quantity-wise.

And below an idea of what we are looking into standard knock sensor specification.

Operating temperature range                  -40℃ to 150℃
Connection Type                                     Cable Type or directly connected with a plug
Characteristic                                           Linear over a large frequency range
Sensing Technology                                 Piezoelectric sensing element   

Brands or Manufacture present in worldwide are ↡      







So whenever your vehicle has issues like 'pinning 'sound, low acceleration, and mileage go immediately to the service center or check your engine knock sensor. And follow company introductions if you have any of them like guide manual. Keep your engine proper service time to time an enjoy long drive. This proper & timely service saves your money and time. And hope you understand the importance of Knock sensor in the engine 


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