07 460, some 8 months ago I put all new PSI sensors on the four driving wheels and also in the trunk

Of course the driving wheels PSI shows up quite quickly on the dash display but the spare tire PSI display takes driving miles to show up

I have gone back to Discount Tire where I had them all installed and they verified their hand held had "woken up" the spare

so how does this all work on my car, one or two driving wheels PSI will come on after starting and just
sitting in the car not moving, so I assume the tires do not have to rotate for PSI to show up

can anyone explain, do the wheel sensors have to rotate or not to show up on display?
how does the spare psi happen to show up, it is not rotating, and why does it take so damn long?
appreciate your experiences and educating me!

 

I too find that the spare sometimes takes several minutes to report after the mounted wheels have reported.

 

Interesting, I wonder what is the cause of that delay. My 2007 has the original TPMS sensors. The tires do not have to rotate to get readings. I was going to type that mine read out within a minute, but I just went out and timed them. The first one came on in 5 seconds, 2 more came on in 25 seconds (one was the spare) and then the other two came on in 40 seconds. I've always had the same metal valve stem caps on. I don't know if it would be faster if I had plastic.

My wife's car has the type that you have to drive in order to get readings. I hate that. You have to drive off to find out if you have any low tire pressure and then turn back home to fill the tire(s).

 

I a had a similar situation once i was cleaning my car i removed the spare tire inflated it and repositioned it and it started working normally -_-

 

"Insanity is doing the same thing over and over again and expecting different results."

Not sure who said this but pretty sure it was a long, long time ago. Maybe way before today's advancements in technology and electronics.
Obviously, this quote does not apply to many things these days, otherwise I'd be insane several times over (however, the debate on this in my family continues). LOL

With computer modules, sensors, electronic switches, and the like, there are several communications going on at once and they do not always act or synchronize in the same manner. How many times have you ever rebooted or restarted something because it did not take the first time? I would imagine the radio frequency waves of the TPMS sensors are susceptible to this. I would venture to say that there is no consistent pattern with regards to the order and/or time it takes for the sensors to read on the display. But as usual, I am open to scientific data or informal driveway testing. <VBG>

 

I use metal caps and it made no difference in how my TPMS vs when I used the OEM plastic (that look
like metal) caps.

 

Avoiding metal caps on TPMS sensors is a red herring. The signal transmission path is through the tire and not via the valve stem. There is an issue with some metal caps because of bimetal corrosion in certain environments. That risk is mitigated by anodizing the caps and putting a plastic insert to thread onto the stem. Most metal caps are OK.

 

Ok so I just went out and put more air in my tires, and because I live at 6000 feet altitude and the air is thinner,
I have to put in 41 psi on my hand held to get the 36 display figure I like to have.
The spare display was down to 31, so I pumped that up to 35.

I don't know guys why it is always my spare tire that reports last and all the time after a least driving a mile.

Maybe those little electrons are all tuckered out having to travel longer from the trunk to the dash display......

reported above that by removing and repositioning the spare tire helped it to report faster, interesting
but I am too old and weak to go back out to the garage and wrestle with the spare

 

My spare is usually the last to be displayed but not always. Most likely has to do with the location and more structure in front of it as opposed to the other four being outward. Maybe try experimenting with different positions of the spare's valve? Hmmm....

 

Same here. Very common to have dashes for the psi reading for the spare for the first few minutes of driving.

 

I've also noticed that the spare seems to report later than the others. After some thought about why that may happen it seems that it is likely related to signal strength. If you think about the transmission paths for the sensors you can see that the spare is somewhat different. The TPMS receiver is located inside the car, on the roof, just aft of the shark fin antenna. At that position there is an unobstructed RF path to all of four rollers because the wheel well liners and internal components are nonmetallic. Occasionally one of the rollers might stop with the sensor/transmitter shaded by the wheel but that is random and unlikely but would occur occasionally. The spare is a little different. Its transmission path is through the ledge under the back window and how it is oriented in the trunk would likely make a difference to its received signal strength. When it is oriented with the valve stem/transmitter toward the rear that would likely be worst case. Conversely when it is oriented with the valve stem/transmitter toward the front of the car that would likely be the best. For those of you who have some interest in this oddity, and little else to do, try that. I no longer own a Lexus so I am unable to help. Keep in mind that the sensor reporting interval may be pseudo random. That is done on some systems to mitigate the effects of signal collisions.

 

Great info! I was wondering and was about to ask if anyone knew the location of the receiver. I just checked my spare, and it's positioned at 2:00. I figured I would leave it as is because, and I may be going out on a limb here, it is the tire that is least likely to suffer a puncture, small leak, etc., so therefore, the one I should be the least concerned about.

 

and jmcrady wins the day! I will try to reposition the spare to it points to high noon

 

Yes, removed my spare tire for driving around town for better mpg.

After 20 min the TPMS system goes into error mode since spare is missing. Any way to fix this and remove spare tire from tpms?
Or does the system REQUIRE 5 sensors? Thanks!

 

Yep, 20 minutes of no report from any one of the 5 sensors will cause the TPMS to alarm. You only get so many of these alarms before it goes to a higher level and alarms as soon as you start the car. The car is designed to prevent you from defeating this warning. Several of our forum members have come up with ways to get around this. I think any increase in the MPG from removing the spare would be very small and not worth the trouble. The most effective way to increase fuel efficiency is to keep your tires correctly inflated and take off slowly, avoid excessive braking and avoid extreme speeds.