Actually, anytime you disconnect the knock sensor on an LT1, the PCM will default to a program that retards the timing under virtually any operating conditions, including at idle.

 

Depending on what the knock module has learned,the more you drive the more the knock module learns and if you loose the knock sensor it will default and use the learned data.If you had a bad tank of gas or for some reason your engine was pinging the knock module will learn and will pulling timing out at the same areas even before seeing knock sensor counts,But you can fix the pinging but the knock module will still pull out timing with no knock sensor counts and sometimes this is burned into the module and you have to replace it.I have seen and done this on several cars and it does happen

 

I am pretty sure the module doesn't "learn". The LT1 pcm doesn't pull timing unless there is a situation causing it(ie. knock). Therefore, it won't learn that it usually pulls timing here and then do that without seeing knock next time.

I have heard of people putting the opti on 180 degrees off or something but I thought it was difficult to do.

 

The knock module is a "filter".... not a Kray Super Computer

 

This straight out of the GM manual "The pcm and knock module learn and can retard timing without knock sensor counts and timing is retarded according to signals from the knock module"Therefore a failed knock module can retard timing without knock sensor activity and not set a code".Maybe the LT1 super computer is smarter than you think.I was just trying to shed some light on the question.Sometimes computers do things that you cant imagine but I have seen this first hand.You dont have to believe it but it is true. Also the knock module is not a "FILTER" but a voltage convertor.It takes a ac voltage and converts to a 5.0v dc so the computer can understand.The computer works on 12.0v dc and not ac therefore could not understand the knock sensors ac reading so the knock module converts this ac reading to a 0-5 volts dc so the computer can understand.

 

Agree.... "the pcm and knock module learn".... the key word there is "pcm". And, looking at literally hundreds of scan logs from these cars, it would be ridiculous for every case of knock retard without advancing counts to represent a "failed" knock module.
But the knock module FILTERS the signals it chooses to convert and feed to the pcm, based on comparison of the noise signature to known noise from other sources in the engine.. ergo the "LT4 knock module"..... still converts/feeds the sensor signal to something the PCM understands, but chooses to ignore signals that match the signature of the roller rockers used in the LT4 engines. Sounds like a filter to me.

 

What they're probably refering to, is when the PCM decides (don't know exactly what will trigger it) you're running low octane gas and goes into "low octane mode" and starts pulling timing like there's no tomorrow.

That's about it as far as learning goes. All the rest of the KR tables, how much timing they pull and when, are fixed in the program. They won't change unless you change them.

 

I also had a very simular problem on the new motor I just got running. My PCM was pulling timing w/ no knock counts. The old motor spun a rod and knock counts were going nuts, Its almost as if retard was burnt into my module. I replaced the module and all is fine. I have to somewhat agree with A&S auto.
I just happened to have an extra pcm laying around I swapped out the module.

Replacing the module would be my 1st choice.

 

Define low octane mode,the pcm does not know the difference,all it will see and knock sensor activity and does not know if its octane,egr valve and engine noise or what ever else,there is not an octane sensor on the car so the pcm does not know what octane you have.The amount it retards is not fixed in the programs,the harder the knock the more timing it pulls.But lets assume that its in "low octane mode" then when you put better gas in the tank how does the pcm know you added higher octane??..And if the pcm/knock module is in "low octane mode" how do you get it out of that mode????

 

There are many sensors and testers to which the PCM does not have access. But it can and does make educated guesses based upon the information provided by what it does have. Of course it can be fooled, but most often that happens when people start modifying things.
The more timing what pulls? The muffler? Or the PCM and the program in it? Maybe, just maybe, that's what all those attack rate, recovery rate, max value vs. X tables in the PCM program are for?
I don't know how much knock it needs to hear before it guesses you have low octane gas and goes into that mode, but when there are three constants and four tables in the program telling the PCM how to retard timing when in this mode, it's pretty silly to claim no such thing exists.

 

I have not seen any distinction between OBDI and OBDII. Is this specific to one or the other, or is this an issue with both?