more knock sensor problems
 

2001 chevy 2500HD, 6.0L, 4x4, 5-speed...

replaced knock sensors 2 times, cleaned the bores out both times squeeky clean, replaced the knock sensor harness also... code still there after being cleared. i just replaced the wires and the spark plugs (someone had put some NGK plugs in there and the gap was at like .070+!, so i put some AC delco iridium plugs back in there and gapped them all at .060 like the sticker says under the hood... after being cleared the codes came back after a few drive cycles. its pulling timing under throttle and killing my mileage and power... this thing is already a pig with the 5-speed so keeping up with traffic off the line i have to mash it pretty good... i can feel it cut timing at about 4k rpm or so... feels like it hits fuel cut or ignition cut. im at my wits end. i check ohms also and they ohm out perfect, the block is grounded good... i just dont know wtf else it could be? computer? i finally have a good job and want to install this vortech v2 charger and can't with this code popping up pulling timing

Have you traced the wires back to the pcm for continuity?

i have not physically opened the wiring bundle and traced the wires individually... i did look over the harness from where the "knock sensor harness" goes into the main harness then to the computer... no cuts or breaks or smashed areas. see the thing is, sometimes the check engine light goes off. if im hauling a car on a car trailer and taxing it down the interstate the check engine light will go off most of the time. other times, like maybe one or two drive cycles a month or so it will also go off and then come back on.

Are you carefully torquing down the knock sensors? I know that it can cause some issues with sensitivity, etc.... if they get over torqued. Can't remember the exact torque spec off the top of my head but it's important to hit that mark.

the first time i replaced them i just hand tightened them, the code came back so i did more reading and found they needed to be torqued down... that is when i swapped them out with some new ones again and torqued them down to spec, also went ahead and bought the harness while the intake was off again. still having same problem.

the thing is, its always both sensors. never just a code for the rear sensor. i also tried running premium gas thinking maybe someone programmed the truck for 93 octane and no luck there either.

You will find a wire or two that are broke inside the insulation. the offender area where I have found them multiple time on customer trucks is in the drip loop between the valve cover and the power distribution block. Always a PITA to find or just run two new wires from the pcm to the knock sensor connector harness.

Your plug gap is way too big. GM issued an update when they came out with iridium plugs. Iridiums should come factory gapped at .040 which is what GM now recommends. DO NOT gap iridium plugs as it damages the coating on them and they will not last then. If you had NGK copper plugs you may be able to go .060 but not with iridiums. The wide plug gap may be causing knock.

any luck fixing it?

I had the same knock sensor low voltage code bank 2 problem buddy. i tripped out and researched the heck out of the fix for a month. Then one magical day on the way home from work the code cleared itself :drive:

dang. so first off i need to go buy new expensive as hell iridium plugs and keep the gap at .040, then i need to look at the section of harness between the vavle cover and fuse panel for the knock sensors? ill have to do this next weekend when im off.