What would cause my traction control light and brake lights to come on?

A few months ago it started this thing where my traction control light comes on, it starts blinking "Service ESC/Service Traction" and it causes my brake lights to stay illuminated even when I'm not pressing on the brakes. I had the brake switch replaced which fixed it for about a month, but it's back to doing it again. Also, it will randomly occur. Sometimes I can drive 10 miles without any problem, but other days I’ll be driving down the road for 1/2 mile and it’ll kick on.
I had it to a mechanic and they can't figure out what's wrong with it. They think it's possibly a bad power steering module. Could this be true? Any opinions are appreciated!