From what I understand, knock is the same as/close to pinging caused from fuel combustion problems.

So somehow the sensor measures this?

Maybe it's able to tell if you got bad fuel or something.

Basically the knock sensors detects "ping" caused by poor fuel/poor combustion conditions. It causes the engine timing to be changed to prevent the pinging which could otherwise damage the engine.

Many cars which say to operate only on premium fuel can run on lower grades of fuel because the knock sensor and other sensors will adjust the engine to run on the lower grade of fuel. The mileage and power will be somewhat negatively affected, but there are those who say they have never run the "required" premium fuel in their engines with no problems.

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It allows the engine to run with the ignition timing as far advanced as possible. The computer will continue to advance the timing until the knock sensor detects pinging. At that point the computer retards the ignition timing just enough for the pinging to stop.

A knock sensor assures that you're getting as much power and fuel economy as is possible from your engine.




knock sensor



The knock sensor responds to spark knock caused by Pre-detonation of the Air/Fuel mixture. As the flame front moves out from the spark plug ignition point, pressure waves in the chamber crash into the piston or cylinder walls resulting in a sound known as a knock or ping. This is caused by using a fuel with a low octane rating, overheating, or over advanced timing. Sometimes it can be caused by hot carbon deposits on the piston or cylinder head that raise compression. A knock sensor is comprised of Piezoelectric materials; Crystals that when impacted, generate a voltage (same idea as a BBQ ignitor). This voltage is monitored by the computer, and when an irregularity is detected, the computer corrects timing in VVT (variable valve timing) engines, or triggers a DTC Diagnostic Trouble Code) in older vehicles.




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The knock sensor is a sensor that detects the point of detonation in the engines cylinders. The knock sensor sends this information to the cars PCM, which makes adjustments to keep the engine operating near its detonation limit and running more efficiently.

Tricia, GM Customer Service.

I get it now, thanks guys