Tire pressure monitor light came on yesterday on the last leg of a 5 hour trip. I checked the pressure and all were within 1/2 psi of each other. I checked agaign this morning and again all w/i 1/2 psi. Reset the monitor as by the book and the light is still on. What gives? Did I lose a sensor on the wheel? It's a 2005 MCS Cabrio.

 

You may have a dead battery in one of the sensors. Go to a good tire store or your dealer and they can plug a devise into your under dash connection and tell you exactly which one is bad.

 

Amazingly my flat tire monitor went off... evidently I was not holding down the reset button long enough. I held it down for 10-15 seconds (just out of frustration) and within 4 miles it blinked off.

 

 

Yes, hold it down until it goes solid (it can take a while some times).

Also, first gen MINIs don't have the same type of TPMS as the 2nd gen cars. We have rotation speed sensors and not an in-tire thingy. As such, the thing can throw a false code if you hit a big bump, or if one tire looses traction or the car slides... for some reason.

I also think that the OBDII system is none the wiser as to which sensor is causing the issues.