Does anyone have a clue what would cause this...If I start my A8 and set the cruise, it works fine. Until I step on my brake or use the "resume" or any other buttons on the stick. If I do, the cruise seems to just shut down and is almost impossible to reset. However, if I shut the cruise off with the switch, I can turn it back on and it sets just fine. In other words, shutting off the cruise using any method other than the switch disables it totally.

 

A8's have way too many systems to just speculate on what it could be, you have to pull the fault codes with a VAG COM or the dealer. It sounds like the brake light switch is malfunctioning, when they do it turns off the cruise control.

 

A8's have way too many systems period - this car is way over-engineered... to the point of uselessness. My car (03 w/35k mkiles) has been to the dealer 4 times since June for the same issue (among others) - Today I'm driving my kid's Sentra since my car died (again) in CT last week.... left it on the side of the road hoping someone steals the POS

I miss my 540

 

While I am not an electrcial engineer, I am a retired comptuer network engineer and am having trouble with the brake light switch idea and am leaning more toward a computer-type issue for this reason: My brake lights work fine and the system shuts down cruise not just when I turn it off with the brake. It also shuts cruise off if I use the "resume" or "Coast" function on the stick.