P0327 after new sensors installed

[masapell]

Vehicle:2000 Silverado 5.3L 236K miles

History: Had a P0332 code come up on original sensor. Checked resistance on both sensors and the front one was around 97ohms and the rear one was at 15ohms. Removed intake and found water/coolant in rear sensor hole and lots of corrosion from water intrusion (possibly from backflushing the heater core a few months ago, as I do not wash the engine bay). Purchased two aftermarket sensors and aftermarket wiring harness and replaced. Torqued both sensors to 15ft.lbs.. Also did silicone dam around sensor plugs, according to GM bulletin. Cleaned all gasket surfaces and installed new intake gasket and followed re-torquing procedures. Started vehicle and MIL extinguished and took for a test drive and all checked out. After several days of driving, daughter reported that the light came back on. Pulled code which read P0327 this time. I checked resistance once again, and both were close to 100ohms each from the connector to the sensors. If I understand the way the knock sensors work, they are similar to microphones, in which they do not receive voltage, they create voltage and that there is a reference voltage that is created during running conditions that the PCM monitors for a high/low threshold. If the threshold is surpassed for a set time, the MIL is triggered. I have read a decent amount of info on using OEM sensors vs. aftermarket. My reasoning was one of cost and the age and condition of a truck that has served my family well and has taken a good amount of abuse and kept moving. I thought that the aftermarket sensors would at least work well enough and built well enough to last a couple of years, which is all I was planning on keeping the vehicle. So, with that in mind, does it stand to reason that the front sensor is not producing the minimal voltage required by the PCM and needs the OEM's to fulfill that requirement? I am assuming that the sensors send a signal to the PCM which then determines by the amount of voltage changes (noise) when spark needs to be retarded. If a misfire condition is present another set of codes will show up? To make a long story (and checking my understanding/reasoning process!) short, this particular problem will be fixed with a new set of OEM sensors?

Any insight is greatly appreciated!!!

[Ol'Jim]

I would like to know if you got the problem corrected?
Did you have to replace the knock sensor again?
Thanks, -Jim.

[j cAT]

the KS code you have indicates with what work you did a bad harness in the KS mounting area. most replace the harness to these sensors.

voltage is low and any bad connection will cause this code.

on the heater core flush disconnect at the block and use a bucket to capture the flush .. when its clean then all is done.
The coolant under the upper intake is most likely due to the GM sponge got disintegrated and was totally gone so any sloppy coolant install will cause this . I used a high temp sealer and covered this on the front of the upper intake slot. left back open .. dam up around the KS pits is good GM did not do it though at factory LOL....

[masapell]

I did get the problem corrected. It was definitely the aftermarket sensors that were the problem. I replaced them with AC Delco ( I should have done that in the first place) and the problem was solved. The truck has almost 240,000 miles and is still going strong.

[j cAT]

post who made those bad KS sensors .. that will be great info ...PITA you had to do this again..

[Ol'Jim]

Thanks Masapell for providing the update. Glad it is cured.
Looks like I am in the same boat. Replaced my rear KS a couple years ago with one from AutoZone. (P0332 code). I was working in Colorado, and I did not replace the harness, because nobody in that area had one in stock. It looked sketchy, but had to reuse it. That did solve the problem for a while. The CEL came on a month ago, and sure enough, same P0332 rear KS low voltage. So I figured it was the crusty old harness. Got one last weekend, (Dorman), and some new intake gaskets. Did the job, CEL went off (probably because I had the battery disconnected all day). 2 days later, it came back on. Same code.
So I ordered 2 new GM/AC Delco knock sensors from Rock Auto, ($41 each, the aftermarket crap ones run $55-65 each). I am getting ready to replace both of them today, and with the new harness, hopefully it will cure the problem for good.

Hey J_Cat, (or anyone else): What are your thoughts on reusing intake gaskets on these LS engines? I would normally never even consider it, but they are $45, and I just installed them 6 days ago. Truck has only gone to work and back 5 days, has not gotten real hot like summer driving. Since they are installed dry, and have the rigid plastic frame and O-Rings in them, and they snap onto the manifold, so they should register in the same exact position, thinking they might be ok to re-install?
The better part of my brain says I have already redone the job once, now doing it again, I should just go buy another intake set. But I don't have backup vehicle to go get them, and don't want to get the engine hot, since I need to get to work on it right away. Your thoughts?
I did take a long time to carefully clean everything up real well last weekend, (Not just the gasket sealing surfaces, but also the heads, intake, engine compartment, etc). Even wiped everything down with brake cleaner and blue shop paper towels. So those gaskets are sitting on a shiny smooth aluminum surface.