I have a 2009 335i Sedan which has the tire pressure sensors. It appears that the only readout from them is a warning if a tire gets 25% low. I'd like to be able to see the actual pressures and temps so I can see a slow leak coming or diagnose a failing tire. Does anyone know if there is a way to compel the car to show the actual pressures and temperatures on the iDrive or trip computer? Has anyone tried using an aftermarket TPMS receiver to read the pressures?
There's definitely a way... but it may cost you. The service tech's can do it to isolate/find a failing sensor... but it may not be able to be done with the on board electronics. A service scan costs about as much as 2 new sensors. I certainly didn't see anything mentioned in the manual about it. There's some secret stuff you can access if you know how through manipulating the dashboard electronics. There is a specific code you have to enter to make it accessible. I was able to do it on my 7's but I haven't had any reason to look into it for the 3 yet. Chuck
Indirect TPMS It is my understanding that your 3 series car has an indirect TPMS that does not use physical pressure sensors. By comparing individual wheel rotational speeds (provided by the ABS), the indirect TPMS determines a deviation of an under-inflated tire due to its higher rotational speed.
Thanks for the update. I guess my 2008 is getting old; maybe they changed in 2009. My owner's manual calls it a FTM and states, "The Flat Tire Monitor detects pressure in a tire by comparing the rotating speeds of the individual tires while moving. In the event of pressure loss, the rolling circumference changes and, thus, the rotating speed of the affected wheel. This change is detected and is reported as a flat tire". Sounds like a indirect TPMS to me.
