The knock sensor picks up vibration and sound coming from the engine block, turns it into an electronic signal and sends that signal to the engine control unit (ECU). The car's computer then judges the information and determines whether or not ignition timing should be altered.

What is inside a knock sensor?

The knock sensor is made up of a piezoelectric element. ... As demonstrated in figure 1, the knock sensor is made up of piezocrystals (piezoelectric elements), a shunt resistor and a thread at one end of the knock sensor, which allows for the device to be threaded into the block near the pistons.

What happens when the knock sensor goes bad?

A bad knock sensor may also not let the engine accelerate properly while driving on the highway, and cause the vehicle to lose fuel mileage. ... Once the computer realizes the knock sensor is not working properly, your vehicle will most likely lose power.