max valid knock, can someone explain?

Can anyone explain exactly what "max valid knock" does? It used to be 12, and now is about 2 degrees. I searched and did not find a clear explanation what it did. I only found that many people copied GM's change to this value - but am not sure they know why either.

There are a few thoughts I have. Is it wise to change this 12 to the new "2" even on a forced induction vehicle? Lets say the car had 4 or 6 dg of real knock at some point due to bad fuel, is this going to limit knock and possibly cause an issue?

Any input is greatly appreciated.

for what vehicle?

I guess corvette Z06 2009 are around 2 and 2006-2008 are 12. Right ?

correct. The exact same change on the escalade 6.2. 12 to 2. I mostly want to know exactly what this parameter controls. Is is update to knock learn? is it only applicable to knock which jumps from 0? I'm assuming GM wouldn't be stupid enough to reduce total knock reduction to 2 degrees. a bad fuel pump would destroy a motor if the appropriate timing wasn't removed for real knock.

it is used as a threshold to set P0326 Knock Sensor Perf, it looks like GM changed the logic on how this one works in later code.

In E40 and early E38, if the knock is greater than this value then P0326 can set.

In later code, If the measured knock is greater than Maximum Knock Retard (table) + Max Step - Max Valid, then P0326 can set. So in later code it's more of an offset below Max + Max Step, than an absolute value, which explains why it reduced from 12 to 2.

Chris...

thanks Chris! Glad I didn't change that parameter for nothing. It would have likely just set a code for bad sensor performance when nothing was wrong. I've seen numerous people make that change, but this just re-affirms it should not be changed.

Sorry for bumping a very old thread, but I just had this exact issue last night. Got a check engine light and P0326 after giving the throttle a really quick burst at lower rpm in a higher gear to make a quick pass that wasn't really planned. I was stressing out about the code until I found this thread.

Having owned an early E38 car, and now a late one, I too was confused by the "max valid" settings for knock. I thought I was being smart changing my value from the factory setting of 2 to 10. Guess I should have realized GM set them that way for a reason. So thanks for this info. Going to change it back to stock right now.