Is there any way to get a brother auto button hole to work on a thick winter jacket

All that comes to my mind is that the button hole accessory needs to be calibrated to your machine. Perhaps that's what your machine needs.

You can download a manual for your machine here:

Manuals SC6600 United States Brother

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does your sewing machine have a buttonhole lever to pull down
before startting a buttonhole?

make sure the needle is inserted all the way into the needle holder
also make sure the needle is turned the right way in the needle
holder

You can download a free manual from the Brother website - http://www.brother-usa.com/manuals/default.aspx?ProductGroupID=3

I believe page 130 of the manual may help - http://www.brother-usa.com/ModelDocuments/Consumer/Users%20Manual/UM_CS_8150_EN_183.PDF

these are the best setting i have found for sewing through thick materials, specifically leather and vinyl:
top tension- between 8 and 9 bottom tension- between 4 and 5 stitch length between 3 and 4 stitch type: 2
that is just what works best for me, i have a brother xl-2600i

You may have to do 2 things press button hole and tell it the size button whole

actually e2 is the button hole lever being down. e6 means that the thread is tangled and to prevent the motor from overheating the machine automatically stops. All you have to do is re-thread the machine and take the bobbin out, untangle it and put it back in and sew. This usually works. If it keeps happening, there could be a few things wrong.

1. if you are using thick fabric your tension should be lower. normal tension is 5.

2. your machine is out of alignment. take it in to a service center, they can fix it in 5 minutes. to find a service center near you go to http://www.brother-usa.com/service/

3. your needle is old or bent and should be replaced.

4. Your needle is too thick, standard is 80. The thicker the fabric, the thicker the needle.