Knock Sensor

[Steve T]

OK, newbie question, what and where is it?

Steve

[Hell Razor5543]

Hello Steve,

I personally cannot help you, but a question that does need to be asked is what is the vehicle?

[addo]

It's a device bolted firmly to the side of your engine block; it contains a piezoelectric crystal plate under slight compression.

The characteristics of this piezoelectric disc (or "crystal") make it very sensitive only to frequencies within a small range, correlating to frequencies emitted by the motor when it preignites. When triggered by suitable frequencies, it resonates in sympathy and generates a small signal voltage which is read by the ECU - indicating that preignition is occurring. In sequence, the ECU then retards ignition timing or increases fuelling - depending on other sensor inputs that describe the prevailing conditions.

[Steve T]

The vehicle is a C5 1.8 petrol, not that it matters now as the question has been answered quite succinctly by addo: thanks guys.

SteveT