The tire pressure monitor sensor (TPMS) light had been illuminated for a while on my 2008 Lexus RX350 even though all my tires, including spare, were at or higher than the recommended PSI. I scoured the web for a solution, but it took me a long time to sift through the many forum posts and actually find one.
There’s actually many things that can cause the problem. I’m posting the information below to help out the legions of other RX350 owners looking for a nice concise solution to this irritating problem.
1. Make sure the Main/2nd button, underneath the dash on the passenger side, is set to Main (this is the “out” position of this push button.) This can easily get accidentally pushed in by a passenger’s leg. If you are wondering what this switch does, it’s for people that have two sets of tires with pressure sensors on both sets. This might be for a set of snow tires, for example.
2. Inflate all tires to at least 33psi.
3. Make sure you inflate the spare tire too.
4. Make sure you have aluminum valve stem caps on all tires including the spare. Don’t use plastic or non-aluminum metal caps. Other metals can actually fuse to the stems over time! You can probably get them at the dealer, but I bought some on Amazon like these.
5. Press the TPMS reset button underneath the dash on the driver side. There are two buttons near each other and it’s the one on the left.
Well, I hope this information helps someone. The Main/2nd switch is what tripped me up and it wasn’t mentioned on most of the forum posts I read.
2016-01-06 – Added picture of the Main/2nd button.
2015-07-20 – Since the Main/2nd button is often the culprit, I moved that from #5 to #1 :-D
2015-10-12 – Amazon doesn’t carry the original caps I bought so I substituted the link and photo to some similar looking ones.