I have an Audi Q5. In November I had a dash warning that there was an issue with the pre-sense system that needed technical attention. I took the car in but no fault was recorded in the memory. Apparently some fault codes are wiped after a period of time. Since then the pre-sense system has twice randomly activated while driving in clear conditions with no vehicle in front at around 30 mph. I get a red warning on the dash momentarily then the brakes slam on by themselves and the seat belts tension. Thankfully on both occasions, there was no vehicle closely following or there might have been dire consequences. The car was very clean on both occasions so I can't think the sensor was obstructed. Due to the potentially serious nature of the fault, I have disabled the system. However on speaking to the dealer, he's advised not to do that but to reset it to its least sensitive setting, otherwise, the system won't record a fault and they won't be able to diagnose what is wrong. So I'm in a catch 22 situation as I'm really worried it will self activate in heavy traffic or while on the motorway. Have you heard of Audi or other makers with a similar system having such potentially dangerous problems? Is this sufficient grounds to reject the vehicle if they cannot trace a fault?