Quick TPMS question...

[goM35]

On my '06 M35x, TPMS reads about 2-3 PSI lower than actual TP. I know this from filling and checking manually. For example, i put in 35psi and the dash reads 30-31 cold and 32-33 hot.

The car is at the dealer right now for warranty work and they called to say the TPMS is acting properly. Any experiences/comments out there that can confirm/deny this?

thanks.

[BrokenTiller]

The EX Tire Pressure Monitoring System doesn't display actual pressure. Just a warning if one or more of the tires is out of range.

[rontek]

I have nnoticed a similar inconsistancy in my 09 FX50S. It's not so much that the cold fill temp does not initially show an accurate reading as the car "calibrates" each time it is started. It's more that the pressures fluctuate quite a bit after driving for a while. Sometimes one wheel will show a pound or two under, and then the next drive it will be fine and a different tire will fluctuate. The only thing I can figure is the TPMS tries it's best to figure the start pressure depending on outside temp and how long the car has been sitting, and then sets a baseline that will fluctuate depending on how far and fast you drive and the temp the tires get up to. That is why it displays all *** until you drive for a little bit. I have come to the conclusion that they are not meant to be an "exact" pressure reading but more of a guide to let you know if one or more tires is substiantially lower than the others. My guess would be there could be a +/- 3 psi range they could be off, maybe more. I don't know for sure, but that is my guess.