check engine lite= knock sensor

[suville]

as the title indicates my check engine lite came on, scanner says knock sensors ok replaced them... within a few miles engine lite again scanner says knock sensors ok well we didnt replace the wire harness first time so replaced wire harness within a few miles engine lite again mechanic say "it a runability issue" ???? ok replaced spark plugs noticed a slight difference in response yup within a few miles engine lite again. WTF Im thinking I could have a knock sensor that is defective but ??? At 95 bucks an hour for shop rate this is getting expensive and Im getting pissed ! Anyone ever experienced this situation and have any recommendations?? Im at a loss as to what the hell is going on with this confusor crap any advise or recommendation would be most appreciated. Thanks

[TBONE1964]

Originally Posted by suville

as the title indicates my check engine lite came on, scanner says knock sensors ok replaced them... within a few miles engine lite again scanner says knock sensors ok well we didnt replace the wire harness first time so replaced wire harness within a few miles engine lite again mechanic say "it a runability issue" ???? ok replaced spark plugs noticed a slight difference in response yup within a few miles engine lite again. WTF Im thinking I could have a knock sensor that is defective but ??? At 95 bucks an hour for shop rate this is getting expensive and Im getting pissed ! Anyone ever experienced this situation and have any recommendations?? Im at a loss as to what the hell is going on with this confusor crap any advise or recommendation would be most appreciated. Thanks

When you replaced the knock sensors, were they torqued correctly? They are 15 ft lb each. They will absolutely get internal damage if not torqued correctly. Did you ohm the original knock sensors? They should ohm 90 to 130 ohms each, of the top of my head. May be 900 - 1300 ohms each.

I have done this job several times on several trucks and some are harder to make go away than others. Parts are so hit and miss on if they are good out of the box. If you drop a knock sensor by accident, you damage it. I see parts delivery people drop parts quite often. It is hard for me to trust any parts the first time around.

Did the rear one of the two have rust on it when you changed it. Did you get one or both knock sensor codes?

Also be prepared for the idea that that portion of your pcm is not happy any longer. Not common but it is possible.

Good luck,
Tom

[Killer Bee]

I replaced both of mine a few years ago due to persistent code.. seem to recall a bulletin that identified updated harness and requirement to seal boots where factory didn't.. also seems I read somewhere that they are vulnerable to moisture trapped by factory foam blocks under the intake that seeps into boot and recommended to leave them out so that cavity stays clean and dry..

here's what mine looked like, before and after.. used all genuine GM OE parts and took me about three hours to get it all cleaned and sealed up, but no codes returned..

don't know if any of that helps or not but good luck!







eta; pro tip, replace oil press sender while intake is off.. of course I didn't but that weak plastic body failed six months later and had an oil geyser under the hood major pita with intake on and cheap enough to replace a predictable failure while access is easy.. it's visible in my pictures just to the engine's left of center, standing up behind lifter valley cover..

[suville]

Thanks for the response guys. I cant ascertain whether or not they were torqued or OHM test I didnt do the work one of the mechanics at the shop did the work. They were very rusty the reason we suspected the wiring harness was compromised so went back and replaced that same mechanic did that. Will keep after this till I get it solved. Thanks again for the input !

[truckdude239]

also make sure to be using ac delo or dephi sensors i used bwd sensor from advance auto 400 miles later light is back on installed dephi sensor has never come back, also with the bwd sensors i had knock sensor code and a cat code after i replaced the sensor with dephi sensors cat code never came back its been 20k miles so far

[Hoods69BadBowTie]

Wow what a pain in the ass I know that not using the oem ac delco ones can piss off these trucks. I have replaced many along with the wiring harness never had any issues. Probably good to torque them I just snugged them n went another 1/4 turn. If they were superman tight when installed or parts were dropped I could see that causing them to go haywire. Let us know what you figure out as I am kinda curios as to what the issue is here as well.

[sleepertruck72]

Originally Posted by suville

as the title indicates my check engine lite came on, scanner says knock sensors ok replaced them... within a few miles engine lite again scanner says knock sensors ok well we didnt replace the wire harness first time so replaced wire harness within a few miles engine lite again mechanic say "it a runability issue" ???? ok replaced spark plugs noticed a slight difference in response yup within a few miles engine lite again. WTF Im thinking I could have a knock sensor that is defective but ??? At 95 bucks an hour for shop rate this is getting expensive and Im getting pissed ! Anyone ever experienced this situation and have any recommendations?? Im at a loss as to what the hell is going on with this confusor crap any advise or recommendation would be most appreciated. Thanks

I agree with previous responses. Use GM knock sensors and harness. Although cheaper in price, Aftermarket stuff seems to never work. Also, I would recommend replace the intake valley cover gasket while youre there already. There is a GM bulletin that says to use engine sealant/silicone around the knock sensor to keep water out of the knock sensor.