Hi everyone. I've been a long time reader here but I finally managed to get myself into a mess that I can't get myself out of. I have an '03 Audi A6 C5 Avant 2.5TDI Quattro. Here's the issue with what I did and what happened: A week ago I decided to order the P21 Osram LED bulbs to make my reverse lights look "cooler." They came, I removed the regular bulbs, put them in and nothing. They didn't work. Disappointed, I put the old regular bulbs for the reverse back on and everything was back to normal. And THEN... My brake lights stopped working when I would hit the brake. Not even the one on the tailgate worked. Shortly after, my glow plug light started flashing and the ABS and ESP lights came on. I saw this thread here: https://www.audi-sport.net/xf/threads/glow-plug-light-flashing.78378/ so I figured something happened with my P21 bulbs for the tail lights/brake lights. I bought two brand new ones (the correct ones) and put them in. They work when I turn on the lights, but still no brake lights when I press the brake pedal and the one on the tailgate doesn't work as well. So I then replaced the brake pedal switch. I bought one as they're cheap and fitted it today. It didn't fix a thing. Still no brake lights. My car doesn't have a loss of power. Everything is normal bar for the lights that are on the dash and the lack of any lights in the back working when I hit the brake pedal. What could it possibly be? Any help would be appreciated.