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Discussion Starter #1
on my 2014 se yesterday, the low tire pressure warning came on,, i did stop the car, all tires look ok, i will check the pressure tomorrow, but was wondering how this sensor works, is it a giggle or level? i need to mention the temp. has been real cold below 0. the lite came on when i was turning a sharp corner,, is this related.. ? also if i do have a low tire and fill it, will the lite go off on its own, or will it have to be reset at a dealer??
 

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"All tires look ok"? There is no way you can measure tire pressure by looking. Buy an accurate tire pressure gauge, not a cheap a** pencil gauge.
WTF does giggle or level mean? The tire pressure monitor sensor in each tire measures the pressure and transmits it to the car's computer which activates the warning light as needed.
Regarding temperature, your tires should always be inflated to proper specs. Yes even if it's 80F and you inflated the tires to specs today, and then tomorrow it drops to 5F the air pressure will drop because the air contracts and you'll need to inflate the tires back to specs. If the next day it's back to 80F, the air will expand making the tires over inflated and you'll need to deflate the tires back to specs.
 

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Tires won't obviously look low until pressures are down to around 15 lb., the sensors will let you know it's down at least 10 lbs. higher than that (exact depends on setting for stock tire type).

Doesn't need a reset once they are aired up, the warning will go away once it sees normal pressures consistently.

Prob. all a bit low, you may find one lower than the rest but check all. Winter weather lowers the pressures as mentioned.
 

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I've read that some systems also measure pressure in the spare tire and it often gets overlooked as a possible warning light cause. Not sure if Ford does that though...
 

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Fords don't use tmps sensors in the spares. Most tpms systems will trigger the light when there is a 10% variation or drop in pressures. So if your car is programmed at 34psi, then if your air pressure drops 3.4 psi your light will come on.

For every 10 degrees the temperature changes, your air pressure will change by 1 psi. So if it's 50 degrees today and 20 tomorrow, your psi will drop by 3 psi. Same goes for increase in temp. 20 degrees today, but 50 tomorrow will increase psi by 3.
 

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This should explain a few things -

http://support.ford.com/maintenance/tire-pressure-monitoring-system-2

What I find odd is that there's no mention of over-inflation, which could be as hazardous as under-inflation. As for the pressure, manufacturers do make allowances for certain variables including air temperature and load. Your starting position should be - inflate tires when cold and with car unladen.
 

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Discussion Starter #7
this is what i love about this site, you get help,, thanks all, Milton' what i meant about level or wiggle, was wondering how, technically the system knows the tire is low?? its gonna warm up, will check today [twothumbs] by the way-- great link Polygon, so it looks like its a wireless sensor, in each tire connected to the stem,,sends the signal. neat;;;;
 

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^^^ yup, direct reading with a sensor is more common than the systems that use ABS info. to figure a tire's low by different rotation speed.
 

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Discussion Starter #9
thanks again to all, i did check the pressure today,, each tire was 27lbs,, yea; all low, but that means no nail ect. i put all back to 36psi, and the lite is gone;;;;;;;;;;;; i really like this system because it could of been a damaged tire.. i did not know each tire had its own sensor sending to the computer.[:)] my 01 gives no warning.
 

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There ya go, just low enough to trigger it for your tire size & recommended pressure.

I'll move this to the Wheels & tires section for reference, most of the TPS questions are in that area.
 

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I just want to comment that overinflation is NOT hazardous.
Yeah 60psi is a big problem. But say your tires are Ford recommended at 35psi. You can with no fear have your tires at 44psi cold. And drive on them. They will feel stiffer, and the ride will be harsh, no question. And if you slam a deep pothole at 35mph.. The tire may break.. On the other hand, at 44psi, the tire may survive better when hitting a pothole than if it was at 35psi.. It is a crapshoot on tire design, the shape of the hole etc..

Anyway, I felt compelled to dispute the 'higher pressures are dangerous' comment. Since I have in the past regularly used a psi as much as 10psi over the recommended pressure. Primarily for handling improvement [hihi]
 

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^^^ Absolutely!

Winter always needs extra air in the tires to compensate for low temps, and there's certainly no need to reduce it on a warmer day when pressures rise. Come Spring normal leakage usually reduces it enough that you never need to let any air out as it gets warmer.
 
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