Code 43 Knock Sensor Circuit Failure Issues

[NomakeWan]

Holy crap. Either you have a ton of knock, or your knock filter is shot, or...I dunno, you just magically have an engine with a sound profile that, over its entire range, just happens to fall within your filter parameters?

I've never seen a knock plot that busy before. That's insane. Even the one time I definitely pushed timing too far (and disabled knock retard), all that happened was I developed a blob in one specific spot. Not a ton of tiny dots all over the entire plot.

[Daveo91]

Generally adding more sealant makes a knock sensor less sensitive, not more. Also usually when looking at knock I look at a scatterplot; it's what Trimalyzer does really well, for example.

dave just curious but what datalog cable are you using?. i read an old post on thirdgen that may be something to consider.... https://www.thirdgen.org/forums/diy-...when-aldl.html

Basically it's saying to use 10K resistor to connect then turn it off once connected. i know mine was always on 10k...

Holy crap. Either you have a ton of knock, or your knock filter is shot, or...I dunno, you just magically have an engine with a sound profile that, over its entire range, just happens to fall within your filter parameters?

I've never seen a knock plot that busy before. That's insane. Even the one time I definitely pushed timing too far (and disabled knock retard), all that happened was I developed a blob in one specific spot. Not a ton of tiny dots all over the entire plot.

Yeah, that's what I'm saying, an insane amount of knock. I really don't think it's truly knocking. It seems I'd hear it and the motor sounds pretty good throughout the range, with the possible exception of WOT at high load. I've asked a couple times in this thread - can it be the L31 roller cam and valve train? Did the vortec trucks use a different KS and/or filter parameters? I also have roller tip rockers but I don't think they'd be causing much noise?

I started playing with my autoprom last night. It's always been finicky with connections both to PC and ALDL. I had to fiddle with COM port settings to get it to connect to PC at all. It eventually connected, but then wouldn't connect again after that. I'm really hoping it's a faulty USB cable, it seems that the connection was sensitive to touching the cable. It uses an old school USB-A to USB-B; I'll have to hunt around in some boxes to see if I can find another one of those.

[NomakeWan]

Did the vortec trucks use a different KS and/or filter parameters?

Every GM vehicle had a unique knock filter, because GM understood that every operating environment was different, so to improve their ability to detect knock across a wide operating range, they tuned each one according to the platform in question. If your knock filter does not match your platform, then it's not doing its job correctly. Either find a knock filter that matches your setup (chassis, engine configuration, etc), make your own knock filter if such a filter does not exist, or as I think I also mentioned before, just disable knock feedback entirely since it's not working correctly anyway.

[Daveo91]

Every GM vehicle had a unique knock filter, because GM understood that every operating environment was different, so to improve their ability to detect knock across a wide operating range, they tuned each one according to the platform in question. If your knock filter does not match your platform, then it's not doing its job correctly. Either find a knock filter that matches your setup (chassis, engine configuration, etc), make your own knock filter if such a filter does not exist, or as I think I also mentioned before, just disable knock feedback entirely since it's not working correctly anyway.

Well finding an exact match is out - no such thing as a square body suburban with vortec, roller-cam 383 running a '7427 PCM. Closer match, I'm not sure. I do have a vortec black box PCM but I have no idea if there's any compatibility there. And making my own filter is probably out, too, since I wouldn't even know where to start. So unless I figure out some other magic solution I may have to just disable knock feedback but definitely not an ideal solution since I'd really like to get closer to perfection on ignition timing.

[NomakeWan]

Generally any tuning place worth their salt is going to have a knock box. It's an external knock processor with its own knock sensor. Mount it to the motor you're tuning, put on headphones, actually listen for knock and tune that way. You don't rely on the ECU to do it for you, you do it yourself.

It sounds like that's the route you need to go.