Knock sensor circuit low signal...

I've been chasing an issue since I've gotten my car running, and it seems like I'm running into a wall every time I try to track down a cause. Bottom line is, about every 2-4th run cycle, the SES pops up and sure enough, it's a P0327 & P0331 indicating a low circuit signal for both knock sensors. The vehicle in question is my '00 Transam with a recently swapped LS3 in it. I've kept the LS3 knock sensors and am running the Racetronix knock sensor adapter (http://www.racetronix.biz/itemdesc.a...1-KSRH&eq=&Tp=) for use with the LS1 harness. I've made the changes to the knock sensor type within my tune (LS2 Flat-response), but as I mentioned I continue to get the random SES with the same codes set. I also logged a little half throttle run on the car and observed each time at approx. 4k rpm, full knock retard would enable, yet beyond that I never see any movement of the knock monitor at all. I know I'm just fishing here, but at the point I'm willing to take any ideas at all because I'm really scratching my head here, thanks!!

That harness grounds to the block - rather than through the PCM. GM wired these to ground via the PCM in OEM calibrations using that type of knock sensor.

Have seen logs of the "on / off switch" knock sensor activity you describe. You need to configure the PCM parameters to work with the response range of the LS2 knock sensors - otherwise they won't work correctly - meaning that you have no reliable knock protection.

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Originally Posted by Taz

That harness grounds to the block - rather than through the PCM. GM wired these to ground via the PCM in OEM calibrations using that type of knock sensor.

Have seen logs of the "on / off switch" knock sensor activity you describe. You need to configure the PCM parameters to work with the response range of the LS2 knock sensors - otherwise they won't work correctly - meaning that you have no reliable knock protection.

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Hmm, ok. I must ask though, when switching from LS1 to LS2 style knock sensors in the actual tune, what are you accomplishing? I figured that would have some bearing on how the PCM interprets the knock signal but I'm thinking that's probably wrong. Perhaps copying an LS2 knock data table on to my LS1 map would be a good start? Come to think of it, I never actually looked at an LS2/3 knock table to know if they're even different..

The easiest route is to install LS1 style knock sensors on the side of the LS3 block. Many have tried to properly integrate or control the LS2 / LS3 style knock sensors with an LS1-B PCM - but very few have actually succeeded.

The typical result of the mix is the manifestation of the on / off switch knock sensor. No knock control, followed by maximum knock retard - which translates into no dependable knock protection for the engine.

+1 for the LS1 style sensors.