Rudybobbo

When I left work today, the tire monitoring icon was lite on my dashboard of my ES 350. Now it was only 20F degrees outside.But this was the first time I have seen this lite up.It stayed on for about 15 minutes.I did eyeball each tire at work and they appeared OK.When I did get home I checked each tire and they were all at 32 or 32.5.So they were all fine.So maybe the cold had something to do with it.I would like to know if anyone else has had this problem.I will contact my Lexus dealer tommorrow.

dreyfus

Did you check the spare? I've had my sensor go on and when I added air to the spare, it went off.

Also, the cold could cause the pressure to drop low enough to set off the sensor. Driving would warm the tires and increase the pressure.

Vette2

I believe that I've read that tire pressures drop about 1 psi for every 10 degrees drop in temperature so I agree with Dreyfus that the cold or a low spare are the most likely causes.

It's worth noting that the system considers "normal" the pressure in each individual tire at the time that the tire pressure monitoring system was last initialized. Unless you've reset it yourself (the button under the dash), that would have last been done by the dealer as part of the pre-delivery service. As has been discussed elsewhere in this forum, some dealers may set pressures higher than the sticker specifies, thus 32.5 lbs. may well be considered low if the system had been initialized at a higher pressure. I haven't seen anything in the manual that tells us exactly how many lbs. a tire must be below the initialization pressure to cause the system to alarm. It might be nice to know that figure.

dreyfus

I wish Lexus would have spent an extra few bucks in their design and had the low tire display indicate which tire(s) are underinflated. Each sensor has an individual id that has to be registered with the car's computer, so it wouldn't be difficult at all for the information to be displayed.

LexBob2

I agree. Last night the low pressure warning display came on in our car. I checked the tires when we got home, but it was dark and very cold around here (single digit wind chill). I think I found the low tire, but will wait until things warm up a bit this morning before doing anything about it. I'm hoping it was just due to the cold weather. It would have been so easy and relatively cheap for Lexus to have taken your suggestion.

<VENOM>

Had this very problem, my Lexus dealer said they get tons of complaints during the winter months, the tires are cold and the light goes on, it's gonna happen all winter, if you do short trips you will constantly see the light, the tires never heat up.

edit: lets not forget when checking the tires the spare also needs to be checked

Vette2

Living in NH as I do, I'm very used to adding air every couple of weeks through the fall-winter cooldown. Conversly, although I still check every couple of weeks, I've noticed that as we go into spring and summer there is no need to add air. The laws of physics apparently have yet to be broken. :-)

On a related note...I prefer to run my tires at 32lbs. so when I took delivery I set them all at that pressure and reset the tire pressure monitoring system. Then I added a couple of extra pound to the spare. Now I have to check the spare only every second or third time and still be confident that it has enough air in it and won't be triggering the monitoring system unnecessarily. Just lazy I guess!

Rudybobbo

Today I called the Lexus dealer about the tire monitoring system problem. He told me that was a common problem in cold weather for the lite on the dashboard to stay on for some time.He said it does reset itself after you are driving for awhile.A guy I work with has a 5 Series BMW. He told me that this has happened to him 3 times in his BMW.Also a lady I work with that has a Chrysler 300 has had this happen to her.All happening in cold weather. So I guess Lexus, BMW and Chrysler do not have their tire monitoring systems perfected in cold weather.

tnedator

Am I reading this correctly. The system doesn't tell you the actual pressure of each tire, it just flashes a light if ONE is low?

amf1932

You got that right!

tnedator

That's pretty lame. When I read it had tire pressure monitoring, I assumed it gave the PSI for each tire.

amf1932

By any chance can you tell me what car will give you all this information, as a factory installed option?
What you're asking for is a very sophisticated monitoring system that would add too much to the cost of the car....although it's a nice idea.

justfixit

This is not a question of perfecting the system by Lexus or any of the other manufacturers listed. Lets remember that this system is in place per NHTSA.
All manufacturers have to have a TPWS as of 2007 model year. The system monitors tire pressures period. It doesnt care if it is hot or cold. Lexus nor any other manufacturer can change physics. When it gets cold, tire pressures will drop. A cold tire at 26psi and a hot tire at 26psi are both seen by this system as 26 psi period. All systems have to notify the consumer when the tire pressure reaches 26 psi. This is the minimum allowed.
Lexus direct tire sensor systems must be initialized properly in order to work properly. Also at some point, we as consumers must take a little responsibility and accept the fact that 26 psi hot or cold will turn the light on.
This system is fairly accurate and simple to use if initialized properly. If you will set your tire pressures to 32psi (cold tires) and then initialize the system, it will set your thresholds to 26psi. This system will set thresholds of 18% loss of pressure when you initialize.
Examples: 18% of 32 = 6 / 32 - 6 = 26 Light on at 26psi
18% of 40 = 7 / 40 - 7 = 33 Light on at 33 psi
If you initialize tires with 32psi your threshold is 26psi
If you initialize tires with 40psi your threshold is 33psi
Lets assume it is 70 degrees outside and you initialize your tires when they are hot and at 32 psi. When they cool off, they will be approx 28 psi. Now the outside temperature drops to 40 degrees. Your tires now will be somewhere between 24-26 psi. Light on. Drive for a few miles and yes the light will go off because psi raised above 26.
If you use the same scenario BUT initialize the system when your tires are cold and 32 psi. When temperature drops to 40 degrees the tires will have 28-30 psi and NO LIGHT ON.
I do agree that the system should tell which tire is in fact low. Other than that, this system works as designed and only as good as it is initialized.

tnedator

Pretty sure my buddies Cadillac CTX shows actual tire pressures.

LexBob2

My initial thought was that it would be nice to know which tire was indicated with low pressure, not necessarily the actual psi in each one. I think this is indicated on some cars.