Good evening
I am looking for a bit of help. My XC90 low pressure light keeps coming on about once a week. Each time this happens I have stopped and had the tire inspected and the tire is fine and so is the pressure. Any idea what is going on? I think I have indirect TMPS system. This last time the guy took tire off put in water and saw nothing.

 

Have you reset the TPMS? - Told the car to store what the current pressures are in Sensus?

https://www.volvocars.com/ph/support...itoring-system

 

Yes I have reset it, I checked the pressure again and its still fine. I even drive it for about 20 minutes. The light has not come back on. But this seems to happen each week.

 

to note, there are two kinds of TPMS systems - prior to 2015 or so, a small sending unit was embedded in the wheels with a tell tale metal valve stem. From that point the TPMS uses wheel speed data to detect low tire pressure (low pressure decreases the rolling circumference so that tire turns slightly faster - enough for the computer to sense). Its possible to get false positives due to things like snow building up in tread or by having a tire that is slightly different from the rest, or due to one of the wheel speed sensors being slightly off (ie dirty contacts, grease on the inside of the hub etc).