Thanks for the advice. Turns out the part only has a 12 month or 12k mile warranty. Bummer.
I had a discussion with them today and basically the advisor said we will have to watch the brake fluid for any worrisome signs, so as to avoid the need for a 3rd master.
Where does the dirt come from that contaminates the brake fluid? There
was a flush in October, another with the master replacement in January
and a third this go around. 3 times in 30k.
I haven't really ignored the check engine light since I bought the car. Various mechanics, including this dealership, have tried to nail down the issue and we will try something and it will resolve the issue for a few hours, days, weeks and the light will reappear. If I remember correctly, the light was on round the clock for the previous owner as well. As the miles racked up, I stopped justifying the need for an answer on this check engine light.