rxets

Does anyone know how it works and how it thinks it's time to warn you?

This morning, I checked my tires pressure, they're 24/26/26/26. Well, if I assume my Tire Pressure Warning System was reset while they're 32/32/32/32, why didn't it warn me the low pressure (during this cold weather)?

One of my tires was 8 psi away from its reset point, or we can say it's 25% lower. What's exactly the mechanism or theory for this TPWS?


Thank You.

PS. I'll reset my TPWS later this week. I can't find related info in my owner manual.

dr_p

the system checks the balance of the pressures, if 1 tire is a set percentage lower than the others the warning light will go off. i assume that due to the normal change in pressure due to ambient temperature, as long as all four tires have reduced equally it consideres it normal. if i remember correctly, there needs to be a 5 psi difference to set it off (most of the time if it happens in the winter it is the spare, as it looses pressure less due to not being exposed)

top up all your tires when cold, in the cold, and hit/hold the tpms button under the dash by your accelerator pedal (need to get under and look up) that should get you set for the winter

rxets

Thanks. That's the interesting theory. As for the tires in the cold, I'll pay attention to.


Actually, all my tires were set to 33/33/32/32 on the day (cold tires; 50F in the garage) prior to my trip to Boston, where its ambient temperature was around 30F (feel-like 25F). I thought my tires would have 2-3 psi less in that environment. Something was wrong, either my pressure gauge or tires, they should be 7-9 psi less.

The G Man

I thought the tire pressure system on the new RX is a direct system, meaning each wheel have its own sensor. An easy to tell is to check the valve stems, if they are metal, then they are a direct system. A direct system should be able to warn you even if all 4 tires are low, that is a big advantage of a direct system over a indirect system.

davesmith

From 2007 & up models, FEDERAL regulation requires that ALL manufacturers to equip their vehicles with a DIRECT TPMS system.

On most Lexus, if it's a full size spare, the spare tire does have a sensor in it, and ALL 5 pressures must be very close to each other or it'll trip the tire light to come on.

If the tire light is staying on steady = tire pressure difference
If the tire light is blinking = you have 1 or more sensors aren't working correctly

Prior to 2007 - some Lexus models used Speed Sensors to listen to "sound" for the tire monitor system. Where you have to manually reset the tire light every time changing tires, adjusting pressures, etc..

The G Man

The federal regulation is simply for a tire pressure monitoring system, it desont have to be a direct system. In fact, many 2010 suvs are going back to the indirect system to cut cost. The indirect system use the speed sensor on each wheel to measure difference in rotational speed, it has nothing to do with sound.

rxets

I believe RX10 has the direct system. RX450 has the way to show all the psi info.

I would love to have the psi info on my panel.

The G Man

I just notice the title should say TPMS, not TPWS. TPMS = Tire pressure monitoring system.

rxets

I'll correct it as TPMS. Thanks.

Lexus makes the inconsistent wording on this. In the owner manual, Lexus seems to use the word "warning" instead of "monitoring" to describe this system. But they do use once with TPMS = Tire Pressure Warning System in this particular sentence below.

P. 534


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rxets

I have no right to change the title of the thread.


MOD, if you see this, please do it for us. Thank You very much.

The G Man

Lol, dont worry about. I didnt even know there was such as term as TPWS. tire pressure warning system. I guess you do learn something new day. Thanks.