You may need a re-build on the ABS/DSC control module. It has a very high failure rate for our cars. That is unless you get lucky and find a faulty or dirty wheel speed sensor. The warning triangle has a curved arrow around it correct? That would be the DSC (traction control) The code 81 is due to the internal fault of the dsc control unit. My 2000 528i does the same thing, and it is also intermittent. I am going to send my unit out for repair. The car will still be drivable and turn around is about 4 days. Modulemaster.com re-builds them for 300 bucks, a new one would be 450 on-line, 1500 from the dealer. And since it is your own unit, no need to tack on another 150 bucks to have BMW re-code it for the car. 3 yr unlimited mile warranty to boot. There are (4) spit torx to unscrew and a wiring harness connector (pulls straight up), piece of cake to remove. Out of curiosity, does your cruise control still work? Mine will rarely engage, and of course, almost never on a long road trip. I think Murphy was a German character, lol.