What does knock sensor actually do?

[bwh13]

I'm wondering what exactly the knock sensors do in the overall scheme of things. Do they trigger the engine program to reduce timing, fuel, etc, or what?

If the check engine light is on due to a knock sensor code, but only 1 sensor is showing to be affected, can I still run the car hard and not expect any detonation that would hurt the engine?

I'm still having issues with my OBDI S52 using a chipped 413 DME. The rear knock sensor code comes up, just by revving the engine, which doesn't make any sense since there isn't even a load on the engine.. Using a stock 413 DME the code doesn't come on, even after driving it around.

All new sensors (cam, crank, knock (2) ) were installed when I did the swap last year. Ran fine with no codes until I had the Vanos unit changed, now this knock sensor code comes up every time I clear it. Starts up with no code, but any rev past 2500 code comes up.

[Farbin Kaiber]

Sounds like incorrect timing @ the.vanos unit. I've seen someone go thru a few m52s from what I assume was a lack of knock sensors.

[e30this]

From what I remember when I was doing some research on knock sensors is you have to make sure you have each one hooked up to the correct plug. Like there is a specific plug for the front and rear sensors.

[hoveringuy]

^^ Correct. There is a channel for cyl 1-3 and one for 4-6. The block rings at a specific frequency that the sensor detects. It then retards timing.

I was kinda wondering how my OBD1 sensors would work on an aluminum block (different frequency?) but seems to be fine so far.

[bwh13]

In what way can the vanos be timed incorrectly?

[e30this]

^^ Correct. There is a channel for cyl 1-3 and one for 4-6. The block rings at a specific frequency that the sensor detects. It then retards timing.
.

See I only learn this stuff because I think this is what fucked my motor up and caused it to run lean.
I didnt know any of this till after the fact. :(