The knock sensor is located on the engine block close to the cylinder head at the Mazda2. This sensor is designed to notice vibrations within the engine from combustion that need to now not be there. Whilst there's continually noise coming from the engine</br> there can be troubles that a regular human ear cant listen. Whilst the sensor tells You that there may be a knock it approach you may have something a good way to purpose damage to the engine. If the sensor gives You a problem code You need to take it to the shop. In case you leave it on my own you could end up with a damaged engine</br> or total failure relying on what the issue is.