froggy1947

I set mine up about 1 yr ago at the recommended 32 psi and did the reset got 3 blinks and forgot about it assuming the technology worked.

This weekend I changed the oil, rotated the tires and checked the pressures which ranged from 25 psi to 27 psi.

Never got any warnings so the question I have is how many psi is this module programmed to require befor a warning goes off?

The lowest tire was 7 psi below my set number of 32 psi.

Does not seem very useful & yes I "should" have used a gauge to back up the technology.

Anyone know? Usually these federal req. things are over conservative but not the one I have.

TIA

kitlz

From my experience, it takes about a 7-8 lb drop before TPMS goes off. And yes, it does work. Maybe the initialization didn't take when you reset it a year ago. The instructions mention leaving the power on for a few minutes after it blinks three times. Try adjusting the pressure and resetting it again.

itiramisu

Mine came on at around 20-25 psi. I didn't even know you could adjust when the indication would pop up...

ISFWes

Not sure about the 3rd gen RX, But on my 2007 RX the TPMS system was a differential type.

If you set all 5 tires to 32. And they all drop 1 psi a month. The light will not come on. As long as all of the tires are the same pressure.

You need one tire to be out of the range of the other 4 tires. Like 5 to 7 psi. That's why when the light does come on. Its the spare or a flat.

kitlz

ISFWes, the 3rd gen RX doesn't have a full spare like the 2nd gen.

I had to use the spare in August after a nail in the rear driver side tire. Yes, the TPMS light went off. I was able to check the pressure immediately (a feature on the 450h). It was 28 lbs. As far as the spare, the tire pressure was 34 lbs. It's supposed to be 60 lbs. After inflating to the right pressure and installing it, I was still getting the 'low tire pressure, check all tires' warning light on the dash. The readout showed 1 lb for the spare. It does not have a warning valve like it used to.

froggy1947

Thanks all, this is an informative thread, for me anyway. What would be nice, I suppose, is if Lexus would take a little effort and actually explain HOW the system works, rather than just how to set it up. I never found anything in the 2012 manual about either.

I'll be checking mine with a hand gauge until there is some clarity on how it works in 2012. These fed rules can change (ugh) from year to year.

GRPFAN

Personally I think the whole system is a big joke.

Hmmm Let me see, 5 tires and one stupid light or low tire pressure warning sign.

Why can't they come up with a system that tells you watch tire is low???

Evitzee

The TPMS is NOT supposed to eliminate proper tire pressure maintenance. Don't assume if the lights don't come on your pressure is fine. A 7-8 lb. drop is significant when it comes to wear, traction and handling. Get a good gauge and check your tires once a month. Unfortunately people are L-A-Z-Y which is why the TPMS system was developed, drivers would never check their tires. For those people who take care of their cars it really is not needed, but for the majority who would never check the pressure it is a feature that may be useful.

GRPFAN

So in the mean time, buyers are force fed to buy something we don't need again.

CapeDave

I just received my new analog gauge from Car Talk. Cannot wait to try it out. There really is no other gauge worth getting. I wish the rest of life was so simple TPMS, no TPMS, who cares? I was taught to check my own damn pressure

froggy1947

No offense meant I agree with evitzee, and grpfan , you are gonna care if/when your state requires it to be functioning as part of registration (mandatory safety ck) and you have to shell out several hundred benjamins to the dealer to get it functioning.

kitlz

Thank you Evitzee for your post. TPMS, or the tire pressure warning system as Lexus calls it, does not substitute manually checking the pressure on a regular basis. It can alert you to a drop in pressure caused by a nail in a tire or other defect. I've had both, the latter being a leak around a wheel weight installed by the dealer. Those are things that unfortunately happen no matter how careful you are. Because of TPMS, I was able to have the tire fixed and avoid significant financial and/or physical harm. Please don't underestimate the importance of properly inflated tires.

CapeDave

You got me there. Of course I want it "working" and to pass inspection. But you get my (4 wheel) drift

armadillo

I am awaiting delivery of my first Lexus RX 450h and am not familiar with the TPSM. Is there any way to check tire pressure? Or will the pressure only ever be shown when the warning comes up?

ISFWes

So on the 3rd Generation RX there is no longer a sensor in the spare. That makes it worse.

I only checked the tire pressure in my old spare when the TPMS light came on. Now you will need to remember to check it at regular intervals. Or when you do get a flat you may have a flat spare tire as well.

armadillo

" I am awaiting delivery of my first Lexus RX 450h and am not familiar with the TPSM. Is there any way to check tire pressure? Or will the pressure only ever be shown when the warning comes up? "

You have never used a tire pressure gauge?