I have a 2004 5.4 XLT 4X4 Supercab with 90K. A while back, the "brake warning light" came on, so I took it in. They said it was the master cylinder, so I got a new one, and the light went out. The light was back on within a week, so I went back in and this time they said it was the switch. So I got a new one, and the light went back on within a week. This happened several times, so I was finally able to convince the tech to look upstream of the switch, as I suspected something was causing the switches to fail.

They did an "end to end", and found that I needed a new instrument cluster. It was done for free, as this was the 5th time I went in for the same problem. The paperwork indicated that test codes B1225-20, U1900-20, and U2013-20 were found. Does anybody know what these are? I was told that this was the first time they'd ever run into this!

And interestingly enough, whatever they did this time not only put the light out, it dramatically improved the driveability of the truck!