Re: Tire Pressure Monitor broken, dealer stumped !
I have got the same problem on a 2002 320ci, after driving for about 15 minutes the yellow warning light comes on even though the tyre pressures are correct. Have read the fault codes using INPA it says that the internal batteries in the sensors are low. I have since found out that these batteries have a life span of about 6 years and can not be replaced, you have to replace the sensor. Using INPA you can see the values of all the tyre pressures and the wheel positions, as the batteries are low the system does not recognise the wheel position so puts the warning light on. Have tried to reset the system and re-learn the wheel positions but it does not recognise one wheel. The senosrs are £72 each from the dealer and the valve stem is about £8.
There is an option to put the system into sleep mode but I have not had any success with this.
Hope this helps.