GAJ said:
Ok folks! I need your participation to help resolve, an erm, difference of opinion! To cut a long story short, do you think that the MINI has an undocumented safety feature which disbles the engine in the event of a flat tyre to stop you driving off and damaging a wheel.
The MINI has no such feature. The whole point of run-flat tires is that you can continue to drive the car even if you have a tire (or 4) with zero air pressure. The flat tire alert system is a totally passive system in that it merely alerts you if it detects a tire pressure problem.
The system does not directly measure air pressure -- there are no pressure sensors -- some cars do it this way, but it's more expensive and requires special wheels. The MINI system does it the cheap way: it uses the ABS wheel speed sensors to monitor wheel rpm. If a tire loses air, the diameter of the wheel/tire will lessen as the tire sidewall collapses slightly. This will cause that particular wheel rpm to be higher than that of the other 3. The flat tire monitor interprets this is a low tire pressure problem and flashes the warning light.
The warning light will continue to flash until the system is reset using the button near the handbrake. The system will not reset on its own which of course explains why it continued to flash even though the car was stopped.
Many of the cars we get here at the dealer come off the truck with the flat tire light flashing because the system has not been initialized (or reset). The car starts happily with the light flashing. The system does not prevent the car from starting and any suggestion to the contrary is simply incorrect.
I don't know what was preventing the car from starting in this particular case, but it was not the flat tire monitor.