Every time a windshield is replaced, or bumper is removed, very important sensors need to be recalibrated. Failure to do so may not cause warning lights to show on your dash, but it will cause the vehicle to act incorrectly when needed the most.
For example, "Audi Lane Assist" uses the camera behind your rear-view mirror to scan for the lines on the road. It's impossible to install it back in the exact spot it was before the windshield was replaced. Its job is to find the lines and calculate placing the car in the middle while you drive. If the camera is off by a couple of centimetres on the glass, that could equal a couple of feet down the road. What does that mean? It doesn't know it's out of centre itself, and will still calculate "middle", but the middle is 2 feet off to the side now, so you'll be driving near, on, or over the line.
Another example, "Audi Pre-Sense and Adaptive Cruise Control" use the radar sensors in the front bumper (those black boxes you see that look like fog lights). If those are not calibrated, similar to the windshield camera, it may think the car in front of you is farther ahead than it really is… and when it comes to emergency braking or following behind another car using cruise control, it may end up hitting the car in front, thinking it had more space.
