more knock sensor problems
06-04-2011, 11:34 PM
#11
or get some cheap copper NGK tr55 plugs and gap to .045-.050 and see if that fixes it
06-05-2011, 09:44 PM
#12
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well thats what the truck had in it... some NGK plugs. i got rid of those quick but they were gapped at like .065 -.070, so i figured maybe thats why the codes are on. so i put some iridiums in and gapped at .060 per the sticker under the hood... the codes that come up say "sensor low voltage" for both knock sensors... and like said if im pulling a heavy load (like a car on a car trailer) down the interstate the CEL will go off. sometimes if i drive it hard all day it will go off momentarily for a few drive cylcles then come back on. i have tomarrow off so im going to check for continuity from the sensors to the pcm... anyone know what pins on the pcm are for the knock sensors?
06-06-2011, 03:42 PM
#13
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i ohm the both wires and got .4 ohms on the "200ohm" scale... could too large of a spark plug gap cuase this? like i stated the light has been on since i got the truck over 15k miles ago. had the NGK plugs in it, gapped at like .070, then i put some Delco iridium plugs in at .060 gap- obviously i need to re-gap those at .040, but i dont notice any spark knock
Last edited by bighoss77; 06-06-2011 at 06:18 PM.
06-08-2011, 10:45 PM
#14
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anyone? i obviously now know that i have continuity in both wires between the pcm plug and knock sensor harness plug. and from there the knock sensor harness is brand new from GM. i have tested the knock sensors right after i put them in and got 100ohms right on the money. ive tried using premium gas and putting in new plugs/wires... only thing left it seems is the pcm?
06-09-2011, 08:48 AM
#15
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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.
06-09-2011, 08:07 PM
#16
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gapping them back to .040 did not help. i left the battery disconnected for hours while i checked for continuity on the knock sensor wires, and re-gapped the irridiums from .060 to .040, after a few drive cycles the light came back on. ill go have it re-scanned, but i already know why its on. i can feel the timing retard at certain rpms when i get on the gas. seems like the truck runs soo much nicer when the light is off... when its on a feel a huge power loss
06-13-2011, 01:17 AM
#17
gapping them back to .040 did not help. i left the battery disconnected for hours while i checked for continuity on the knock sensor wires, and re-gapped the irridiums from .060 to .040, after a few drive cycles the light came back on. ill go have it re-scanned, but i already know why its on. i can feel the timing retard at certain rpms when i get on the gas. seems like the truck runs soo much nicer when the light is off... when its on a feel a huge power loss
06-13-2011, 07:18 AM
#18
I had similar problem twice. Low signal codes for both sensors. First time ground had a painted bracket between block and ground after transmission swap. Went through all you went through and more before I reinstalled ground straight to block. Problem solved for a year. Problem came up again a few weeks ago. Checked ground but "looked" okay, still tight. Checked everything else (ohms, pcm connections, etc.), but still had problem. Finally took ground loose, looked at it, tugged it, pinched it, couldn't see a problem, reinstalled it, and problem has been gone for three weeks. An insulated broken wire or corroded mating surface can be hard to "see".
02-22-2014, 10:39 PM
#20
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I'm going through them same thing. New harness, sensors. Just install a new set last night was throwing a p332 code for the rear I have fix this for the second or third time so far it has not came back on. If it does I'm taking it to the tuner and having him turn them off. The hell with that damn code and the damn knock sensors. My truck is a 01 scsb 4.8 it's slow enough with out that code. Man if you find out what this is let us know.