Ok, so I purchased my cmax with the intent on using it to move the family around in a nice quiet environment. It was all fine and dandy with just me in the car but as soon as I had a passenger it would randomly have horrible resonant frequencies that would drive me/us nuts. Well, eventually I figured out this was a known issue that plagues many of these cars, I verified it was indeed the ANC by tapping on the microphone when the annoying note was blaring in the car and it momentarily shut up. My first thought was to find the fuse for it and pull it. Sure enough there is a fuse in the trunk that is labeled ANC in the owners manual. I pulled it and it did absolutely nothing, the active noise cancellation was just as cranky as ever so I started my quest to figure out how to disable it.
Anyways, I was able to access the ford online database (thank you coworker who shall not be named) and checked out the wiring diagram for all the interior body stuff and figured out where all the microphone leads should go into the big module that controls all the audio integration. Found the plug, unplugged it and went for a spin! No more horrible noise! Completely defeats it with literally no other affected areas.
This procedure is absolutely critical if you ever decide to add a subwoofer onto your stock system as it'll play ANC tones through it at massive volumes if you do not
Onward to the actual how to:
Open your passenger door and put the passenger seat all the way back, you will be on the floor under the dash.
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Stick your head under the glove box (leave it shut) and notice there is a thin fuzzy panel that is retained by two black clips that go over yellow posts. Remove the clips and pull down on the panel so you can see behind it. You should see a fuse block, some wiring, a floor light, a floor vent, and some various other stuff.
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Locate the gray 6 pin plug that I show in the image, all the primary wire colors are blue or brown as shown. If you need the supplementary wire colors for some reason just ask and I'll catalog them but it's the only plug that has this color combination in this direct area. Unclip it! If you are worried for some reason, you can wrap the end in electrical tape or something but they are heavily recessed and should never have any issues with touching anything.
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Put the furry panel back into place and stick the clips back over their posts to hold everything together. You know, the whole reassemble in reverse order thing.
Enjoy your lack of Skrillex inspired wobwobwob!