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Thread: Knock sensors...
01-13-2011, 12:28 PM #1
Check engine light came on this morning... took the truck to the High school auto shop and let them look at the codes while I worked on computers at the campus... anyway, I came back to find out that it was the knock sensors. They cleared the codes and told me to see if the CEL comes back on.
Now.. I went ahead and priced out the parts.. kind of... I dont know if I have 2 wire sensors or 1 wire sensors... and the price difference.. WOW! The 1 wire sensor was like $55, the 2 wire sensor is like $10.
Any ideas on which ones I have, or how to tell the difference (without taking everything apart)Matt
Wichita Falls, TX
2007 Chevy Silverado 1500 Classic LS 4x4, 4.8L
Thrush Welded muffler, dual exhaust
HELO MAXX6 18" Rims, Torza Tri Fold tonneau cover :glasses:
01-13-2011, 03:33 PM #2
Had this same code come up this past summer. Cleared the light, and 4 hours later it came on again. Then early the next morning it went out by itself. Chances are you can actually get away with just cleaning the sensors.
Sorry I can't help you with which type you have. But if you know the location and are willing to take everything apart, I would suggest doing that and use a good sensor cleaner like MAF sensor cleaner or anything else by CRC to see if that solves your problem first. At the same time you will find out what type of sensor you have. I believe the easiest way to tell is at the connector end. If there are two pins that means 2 wire, 1 pin = 1 wire.SEAFOAM, I PUT THAT @#!$ IN EVERYTHING!
2004 Silverado LS 5.3L Z71 Crew Cab
01-13-2011, 03:58 PM #3
I believe they are under the intake on my truck... the reason the mechanic told me I would have to purchase intake gaskets....
01-13-2011, 04:29 PM #4
try calling the parts department at the dealership, they should be able to tell you which one it is, probably based on vin.David
2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
1960 Land Rover Series II 88
2002 Nissan Altima (My Commuter)
2013 Toyota Avalon Limited (Wife's Car)
NRA Life Member
01-13-2011, 04:33 PM #5
i had this same problem on my '02. The CEL would come on for a few minutes then go off. Each time it came on it was for longer periods of time though. Granted it was about a month between each time. Now it just stays on. I don't really want to have to take the intake off and deal with that, so I just check the code about once a month to make sure no new codes have come up.2002 Chevy 1500 Ex-cab Z71: 5.3L, auto 4, shorties, hi-flow cats, true dual 2.5" straight pipes, AirAid intake, TBS, Platinum plugs, 8.5mm wires, programmer, 3in w/ 33s, also has the composite bed
2010 GMC 1500 Crew Cab Z71 w/ All Terrain package: 5.3L, auto 6, 2" Zone leveling kit, AirAid Jr. Intake Kit
01-13-2011, 08:34 PM #6
I've heard that on occasion the cause of this can be knocking lifters. The problem is at startup, while the oil pump is building pressure and getting oil up to the top of the engine the lifters knock a bit and can be loud enough to cause the sensor to be tripped. The other possible cause is that ever familiar piston slap many GMs have during warm up. The best thing you can do to avoid this issue from startup is to let it idle for a few minutes (not just the 30 seconds it takes you to put your seat belt on and think about where you're going to go) before leaving your parking spot/driveway.
This should only be an issue with an oil pump that might be losing it's prime causing the delay before the oil can get to the top of the engine.
01-14-2011, 09:32 AM #7
The light was off all afternoon yesterday, when I drove it around. This morning (when it was cold again) it came on about 20 minutes into my drive to work. I always start my truck 5 minutes or so before I leave the house when its cold.
I am not going to worry about it a lot, maybe Uncle Sam will owe me some money and I can get it fixed...
01-15-2011, 06:24 PM #8
Some guys on this site have had this problem after installing non-A/C Delco spark plugs.
01-15-2011, 07:40 PM #9
01-16-2011, 01:26 PM #10
The problem is not allowing the truck to warm up or non ac delco plugs. The problem is the 2nd, or farthest back, sensor. Water gets into the sensor recess and causes the sensor to malfunction. The pieces of foam at either end of the intake that are supposed to keep water out from under the intake do not do a good job. GM also didn't silicon the rubber covers that are on top of the sensors, so water can easily get in there. The only way to keep the code from coming back on is to replace the sensors. While your in there replacing the sensors, you're gonna have to replace the intake manifold gaskets. You will also most likely need a new knock sensor harness since they become brittle. Also, since your down there, replace the plenum gasket because that area typically has an oil leak. I'm going to do the knock sensors on my brother's 04 and my 00 probably during spring breal. I'll probably do a write up on it if we need it.2010 Equinox LT
2.4, 6 speed auto, power lift gate, remote start, bluetooth, xm.
1995 Cheyenne C1500 ext. cab(my baby, my first truck)
5.0, 5 speed, Silverado appearance package, power nothing, bucket seats and console Silverado, painted black interior, eBay halo headlights, eBay chrome tails, eBay cai, dual Flowmaster 40's w/no cats, 15x7 American Racing Hopsters, Walmart fog lights, SS mirrors
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