Canadian Hummer Club Forums

Okay, had a check engine light come on this week and I checked all the usual things like tire pressure balanced properly, bad gas (purchase all the time at the same place), clogged tailpipe, etc.... Nothing seemed to help. Eventually I ran it for a code and received a P003332 which is the Knock Sensor. Anyone ever come across this one??? Talked to Olishooter and he suggested bad gas and try high octane gas which I will do once the tank is almost empty. The also stated it is not common and he would like to investigate before changing the sensors (a 3-4 hour labour as the location of the sensors dictate taking the intake right off and out). Also talked about checking the wiring harness and wire first to see if a mouse or chaffing had damaged the electrical....need service manual instructions for this one as I am not familiar with the placement of the wiring harness that feed to the sensors.....



Any help or assistance would be greatly appreciated as the replacement of the sensors is looking to be between $700.00 - $1,000 for a part that is just less than $100.00.

I've heard of this popping up before and I think GM had a TSB for all applications of the 5.3 and 6.0 V8, although I can't find it at this time... There's two knock sensors under the intake manifold that are not well sealed from water, the boots/gromments get brittle and crack allowing in some water, and the rust that accumulates can get extremely bad. Eventually this code is thrown!



With the intake off the sensors are easily accessible but it might take some patience getting them out due to the rust, the fix would take you a few hours if you go the DIY route but it's a simple process. Probably bet on replacing both the sensors, the back sensor tends to die first but the front isn't usually far behind. With the intake manifold off just make nothing falls into the exposed intake ports on the head, so seal them off with some tape as soon as they're open to prevent an accident!



The TSB also recommended sealing the new grommets with some RTV to prevent more water getting in, sealed up and ready to rock for good! Whatever you're most comfortable with of course, but I'd say this is a good candidate for a garage DIY fix.



I hope this helps!!

[quote name='JL' date='01 August 2010 - 10:26 AM' timestamp='1280676414' post='19878']

I've heard of this popping up before and I think GM had a TSB for all applications of the 5.3 and 6.0 V8, although I can't find it at this time... There's two knock sensors under the intake manifold that are not well sealed from water, the boots/gromments get brittle and crack allowing in some water, and the rust that accumulates can get extremely bad. Eventually this code is thrown!



With the intake off the sensors are easily accessible but it might take some patience getting them out due to the rust, the fix would take you a few hours if you go the DIY route but it's a simple process. Probably bet on replacing both the sensors, the back sensor tends to die first but the front isn't usually far behind. With the intake manifold off just make nothing falls into the exposed intake ports on the head, so seal them off with some tape as soon as they're open to prevent an accident!



The TSB also recommended sealing the new grommets with some RTV to prevent more water getting in, sealed up and ready to rock for good! Whatever you're most comfortable with of course, but I'd say this is a good candidate for a garage DIY fix.





I hope this helps!!

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Hey man, thanks....I'll look into it when I get back from Florida..mechanic said that I would be okay until I got home....

That is some good crud in there for sure! But great photos as it goes to show how and why the sensors suffer. You'd think they're well protected down there but clearly that is not the case!!

[quote name='Hummeron37s' date='02 August 2010 - 09:41 AM' timestamp='1280760076' post='19886']

Knock sensors are very common on the 6.0L I had to do mine not to long ago. It took about 3 hours in the driveway and can be done by anyone who is not mechanically illiterate. When I took off my intake the knock sensors were submerged in water and I had about a 3" thick wall of dirt in the valley. I suggest changing both sensors and both connectors while you are in there.









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Excellent post...the pictures are great. Say, about a week before the chech engine light came on, I had the H2 almost stall when I came to a stop in traffic. Did this twice, but never again. Is this something you have experienced when your knock sensors went?? I just don't want to miss something and have the vehicle running rough because I may have overlooked a problem related to the knock sensors.

[quote name='Hummeron37s' date='03 August 2010 - 04:51 PM' timestamp='1280872310' post='19919']

When the knock sensor code comes up the PCM goes into what they call limp mode. It causes a major change in how the truck will run. It is possible that the sensors were going and the PCM was compensating. My suggestion to you is to clear the code and see if it comes back, if it comes back I would replace both knock sensors and both connectors.

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Cleared the code and it came back...noticing the Hummer has less power uphill and off from a dead start so I'll be replacing them once I am back from Florida...