hi there i have a 2007 leon cupra, the car is equipped with the tyre pressure monitoring system, it has the yellow light on the dash when first turning the ignition on and then goes out and also the button in the centre console. you can hold the button and the system will reset with a bleep and then the light goes of on the dash. anyway havnt had the car on the road long at all and had prevously checked my tyre pressures and reset the system, but the next day i noticed my o/s/f tyre was soft about 20psi but i didnt get any warning or signs of this problem whilst driving the car or anything at all which indicates to me that something not working properly??? what pressure does the tyres have to drop to, to get a warning from the system??? where are the pressure sensors on the wheels are they internal on the wheel itself or are they the in the special valves you see on other cars, the valves look like normal rubber valves with no steel sleeve or solid base like you normally see on cars with pressure monitroing, im thinking the sensors or valaves may have been removed when tyres have prevously been fitted, would the system not work if say only 3 valves were present or something??? the other interesting thing is that i have a bosch diag machine at work and went into the car config, the tyre pressure warning option was set to NO???? i reset it to yes thinking this would solve the problem but i then just got a error on the tyre system saying there was no signal or sensor readings, which is why im thinking the sensors are not all present if any???? any ideas or ways of identifing pressure sensors on the wheels is great help???