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GMT-800 Knock Sensor and MAF engine codes

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Posting this for my brother to help him out. He has a 2007 Silverado 1500 5.3l classic with like 140,000 miles on it.


He recently came back from a hunting trip and it's now throwing some codes. I'm getting him to get me the specific numbers later today but he said MAF sensor, and the knock sensor codes. Also said something he has codes for both engine banks being rich.


So he started out with replacing the MAF sensor and since that was easy to do. Cleared the codes and started it up and the MAF code popped back up. WTF?! Not sure why replacing that wouldn't fix at least that one code unless there's something else that's throwing all of the other codes.


The knock sensors I assume are probably bad like there are so many topics about. I suggested he go ahead and replace those and do the RTV trick. He did say while hunting he did go through some deep water so that may have caused a few issues.


And to top it all off, he's getting the best gas mileage he's ever gotten. So it being something like an O2 sensor (which I wouldn't understand cause I'd expect it to throw the specific O2 sensor code and not 5 others...) or something. So, um... Help?



As mentioned. I will have the specific codes a little later and can get more specifics on a few things if that helps. Thanks.

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The water scdewed the knock sensors. Replace sensors, wire harness, and use RTV. The MAF could be in wiring. A screwed up maf signal will cause it to run rich or lean


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  • 2 weeks later...

On the 2007 classics, is the knock sensor still located under the intake manifold? The GMT-900's (2007+) all have them on the side of the motor. My brother's maintenance books just lump all 2007+ silverados together which would technically include his. He spent 2-3 nights working on replacing the sensor and can't even find the damn thing. Makes me think the book screwed up and forgot about the classic which is basically a 2006 truck. Which would also mean they're under the intake manifold.

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I have seen this before MANY times as far as the knock sensors go and my advice would be to get either Delco or Delphi sensors, and get a new harness as was mentioned above. One little trick is to remove the foam that they put under the intake as it causes water to pool up under there and fill the sensor wells. DO NOT overtorque the sensors they will be damaged and you will have to pull them back out again. I think the torque spec is somewhere between 16 and 20 ft-lbs, but don't quote me on that. I can do the whole job in about 2 hrs, but as a first time I would plan on 4-5 hours, and you will need fuel line disconnect tools for the lines running up to the rail. As far as the injector harnesses go, you will need to disconnect them and they are really stupid on your model year. They are fragile when cold, if they are under 60 degrees F they break easily when removed, so to make this easier, warm them up a little with a hair dryer before removing them (you have to squeeze the connector and pull and wiggle GENTLY to get it off the injector). As far as the MAF goes, it sounds like it may be either an air leak or a wiring issue. and for the o2 sensors, if your rear most exhaust bolts are broken off (very common on those) it can make a good o2 seem faulty. However, it may just need some new o2s. Sounds like you have some work ahead of you! Grab some beers and dig on in, it's good learning!

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