jer

My TPM light went on coming into work this morning. I did a visual check, everything looked ok. When I got to work got out the old gauge and they all show about 28 psi. The manual states it can go on due to 'natural causes' but doesn't really go into detail. Does anyone know if it goes on if any/all tires fall below a certain psi? I'll be going back out later to check again to see if one of the tires is going flat. thanks all

RickC5

Did you check the spare?

jer

Didn't check the spare- my manual states that in using the spare the light would still stay on, so it wouldn't have tpms, or is that not correct?

jfelbab

28 psi on a hot tire is very low. If measured cold it could easily be 4-5 psi lower. Your tire pressures will change 1 psi for every 10° F of temperature change. Any reason you have the psi set so low? Lexus recommends 30 psi for the 2004 RX and 32 psi for the 2014 cold. Why not add a few pounds of air to the tires and see of the TPMS is happy. You didn't mention which RX you had this issue on, The 04 doesn't use actual tire pressure but looks at wheel rotation differences to trip the alert.

jer

Sorry, it's the 2014. Yes, I noticed it was low- had been lax in checking the pressure on this one- had been probably over 2 months. Will be going out to check later today and as long as no flat will reflate when I get home. thanks

MDames2

iTrader: (1)

To answer your question. Yes, there is a minimum set pressure that will trigger the TPMS if any tire falls below that. You can determine what that minimum setting is when you do a reset of the system. Look it up in your manual.

silverar

I live in bahrain and the temp is around 35-55C how much psi should i put ?

Super Blue

I believe 28 is the low trigger. It is on my 2010.

jfelbab

When your car has not been driven for a few hours and the tires are cool, set the tire pressure to what is displayed in your drivers door or owners manual. It is typically around 32 psi.

Tires pressure should be checked every few weeks especially as the climate changes from season to season. Tires will gain or lose pressure at a rate of 1psi for every 10° F of temperature change.

jer

Last night after work stopped & put air in, checked and tires were all from 28psi-30psi. So 28 being the low threshold would do it. I got them up to 32psi and reset the TPMS. So looks like it was just that the tires were starting to get low. Nice to have, but I'll definitely get back into the habit of doing the monthly check.

kitlz

Usually the TPMS light will go off after the pressure drops 6-8 lbs from the point of reset. So you might want to boost it up higher, reset the TPMS, and lower to your desired pressure. That way the tire doesn't get down that low. I've had the light come on anywhere from 28 to 31 lbs. The number isn't necessarily set in stone.