Ratatat sound is caused by a pinion gear connected to two flexible racks. In my case, a spring clip had lost enough tension to stay in place. [br]
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First you have to get to the motor/pinion/rack. To do that, you have to pull down the headliner a bit. Remove the overhead light module by using a knife/fine screwdriver edge to pop off the plastic covers on the lights. Remove the plastic reflectors. Then you'll find part of a metal clip inside there that you need to pull on and then push through the hole so that the entire button/light assembly will pop out. Some youtube videos sort of give you some of the idea.[br]
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I removed the sun visors and sun visor holders. Very annoying to remove without special tools. This guy helped out there:[br]
https://www.youtube.com/watch?v=CineCUPeUxM[br]
Screw drivers didn't really work for me. Instead, two paint can-openers have the right shape to apply a force on either side to unclip them.[br]
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I removed the headliner trim piece surrounding the sunroof hole. This covers a long piece of metal that has parts of it shaped as clips. Pull it away from the edge to let the headliner drop a bit. [br]
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With access from the overhead light assembly and access from the sunroof area, I was able to remove the 3 screws holding the motor assembly in place. The motor assembly has a pinion gear coming out of it. There's a flexible clip that provides tension two the two flexible "racks" that connect to the sunroof assembly. I noticed that the flexible clip would pop half-way out if I tried to put the motor/pinion in and press the button. With pliers I bent the clip to provide more tension to stay in place better. After I put it back and put the motor assembly back, it all started working. Note that you have to check where the buttons think the sunroof vs where it actually is so that you don't cause it more damage or confusion. The pinion gear pulls it closed and then stops, but if you press the tilt up button, it continues pulling in that same direction. This spot between starting the tilt and fully closed corresponds to the peak of the rails that you can see the sunroof itself riding on so I aligned each to that spot.[br]
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One other thing to note is that I did remove the 4 T25 screws that hold the sunroof in place in case the rails/motor would try and send the glass to a place that would damage it as well as to adjust the height/fit of the sunroof once I got it to the spot I wanted. It's very easy to access those 4 screws without touching anything else.