My car suffered water ingress due to a drainage pipe getting blocked with leaves - the result was that the area where the battery sits in front of the windscreen filled up with water to at least the underside of the battery - the water then found its way into the front footwells through the bulkhead which is what alerted me to the problem (also occurred on my previous A4 so seems to be a design fault). Anyway, the water appears to have affected the electronics controlling the tiptronic gearbox. For a short time the car went into a sort of limp home mode where the throttle didn't react and the car would only move at idle speed. After a few hours, it worked again, but when I switch of, all the lights on the gear selector indicator on the dashboard light up at once, and using the manual select facility has no effect. I thought it might fix itself once it dried out but so far it seems to be a permanent fault. Can anyone advise where to start looking - I suspect there will be some sort of plug in electrical unit in the space near the battery that has been soaked. I should add that the gearbox works after a fashion in D and R although when you select them there is a jerk, and also it won't get into fifth - 40mph it's still doing 2000 rpm which is what it usually does at about 60rpm. 5th usually cuts in at about 37mph. Car also a wee bit slow to pull away with more slip than usual.