Steve - On diagnosis only for a customer yesterday I saw a similar problem on a 2000 W210 E320T, we pulled the codes and had something like
xxxx-brake light switch
xxxx-Brake light switch (plausability vs. brake assist)
I presume this is to do with the brake assist function. Is there a simple switch on the brakes for that, or do they use something to guage how hard you hit the brakes, and/or how quickly you come off the pedal, and was that the problem being suggested by the machine?
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black