Low Tire Pressure Light

C

claydoctor

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This came on last week and I panicked as I have already lost two tires to nails. Checked all the tires including spare and all were 30-32PSI. Light stayed on about two days, then went off for two days. Now it's back on. I'm taking it in to be checked but my salesman tells me that if any one tire is more than 2 lbs off the others, light will come on. Is that so? If true, it would seem to be a true PIA trying to keep all tires within 2 PSI of each other. By the way, I have 28K on the truck and this is the first time it has been an issue.
 
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The salesman is wrong; the 4Runner has active tire pressure sensors in the valve stems, so they're reporting absolute PSI to the computer via a wireless transmission. The light comes on if the pressure in any one of the five wheels drops below 27 PSI. The relative pressure doesn't matter (they don't need to be within 2 PSI of each other).

In the winter weather, you need to account for the fact that pressure will drop in the cold air by about 1 PSI for every 10 degrees. For example, if they're at 30 PSI in your garage at 40 degrees F, then outside at 10 degrees F they'll be 27 PSI and the light will come on.

For more info, you can search on "TPMS"; there are a lot of threads on this subject.
 
shit I was thinking that. don't want to change it as I am saving up for new tires.
The stock one are BS for what we pay for.
 
blk05runner said:
shit I was thinking that. don't want to change it as I am saving up for new tires.
The stock one are BS for what we pay for.
Click to expand...

No reason your spare shouldn't hold air along with the others. It is a little tricky checking it's pressure w/o removing the tire but it's do able
 
My TP light comes on every time the temperatures drop below 30. I had it in to the dealer yesterday for an oil change and they said this was common.
 
My tpms light came on a few weeks ago when I went up to the mountains to snowboard. I was a little surprised that it did because I normally run my tires around 36-38psi front and 34-36psi rear (spare is normally around 40psi so I don't have to check it too often). I didn't think that the temperature drop would be enough to trigger the light, but it did. After about 30 minutes of driving on the way home, the light went off.
 
i had my TPMS light on for a few days , checked 4 tires, all 4 at 34psi, so i checked my spare, guess what? its at 25psi. pumped more air to it and light's gone.
 
That's all the dealer says he did to mine today, set all tires at 32. Well when the liight came on, I checked them all and they were 32 except spare which was at 30. While I was waiting for my ride from dealership, someone else brought his car in and I overhead same story, "My tire pressure light won't go off".
 
I had this issue for the longest time! The Dealer told me that it will do this if the temperature is cold enough! I live in texas so once it gets below like 45 mine comes on, but then once it gets to like 45 or above it goes off. So I wouldnt worry about it as long as it goes off on its own!
 
The follow-up is that when I got it back from the dealer, the only thing on the ticket was "inflated all tires to 32 PSI" Well I had already checked every one and they were right around 32 PSI give or take a pound, including the spare. Maybe it was the cold. The light has not come back on.
 
I had this problem as well...until I asked the around to see who could fill the tires with Nitrogen (N2). Turns out the dealer can do it for $30. I have had it for about a year and no problems. I put on some locking valve caps to keep them from getting "accidentally" adjusted.
I was surprised they didn't say something before when me (and just about everybody) was having problems with the damn TPS. Turns out the service person "had no idea" (Imagine that...)
(I wish the service personnel had to have at least some basic auto shop education.)

But the bottom line is I have had no problems with the TPS, especially with the temperatures fluctuating so wildly this winter. And the tire pressure hasn't varied at all. I used to check it everyn month...now I only check it when I rotate them...every 5k miles.

N2 is also supposed to treat the tires better by not heating up like regular air and preventing corrosion problems of the valve stems (and TPS) with the moisture in it.

$30 seems like a decent preventive cost for $800 worth of tires. (Bridgestone Revos)
 
$30 is a RIPOFF to fill with nitrogen IMO. Regular air already consists of about 75% nitrogen so getting charged for that extra 25% seems like a lot. It's your money so feel free to do whatever makes you happy, but I just can't justify it. People have been filling their tires with regular air for decades so I'll continue that trend. If they fill with pure N2 for free, then I'm all over it.
 
Well...before I had to fill and adjust my tires regularly...I would say every couple of months...with air (~78% N2, ~20% 02).
With that...tire pressure would fluctuate enough on colder days to warrant the TPS going off.
Now the TPS does work the way it should...it isn't just an annoyance. And after checking the pressure would find it was around 28PSI. So, due mostly to temperature change, my tires had lower pressure.
Schraeder valves do have issues with regard to maintaining pressures...but they aren't nearly that bad. So the conclusion has been to fill tires with a single, inert gas to maintain a more constant pressure.

IMO, I would gladly spend $30 to insure my tires maintain a constant pressure. It sure beats having to go to the station every couple of months (or more during the winter) to adjust the pressure. If nothing else, to insure the safe(r) drivability of my truck.

I have certainly seen more frivolous spending for questionbale return.
 
sharp4runr said:
$30 is a RIPOFF to fill with nitrogen IMO. Regular air already consists of about 75% nitrogen so getting charged for that extra 25% seems like a lot. It's your money so feel free to do whatever makes you happy, but I just can't justify it. People have been filling their tires with regular air for decades so I'll continue that trend. If they fill with pure N2 for free, then I'm all over it.
Click to expand...

Probably appeals to the bottled water crowd.
 
Never accept cold weather as a cause for malfunctioning TP indicator. The TP monitor should be functional to -40^ and not erroneously signal (given all tires maintain a minimum pressure).

100% nitrogen fill will not affect your TP monitoring system (or your tire pressures btw, but that's for another thread).

My TP monitor has caught two tire leaks (a screw and a piece of wire) that otherwise weren't noticed. While the tire makers aren't happy with the current "gross" leak TP monitor requirement, I have found the system valuable.
 
The indicator isn't malfunctioning. If the light's on, one or more tires is below 27 psi. Just because the tire pressure is "fine" in the warm garage doesn't mean it's still fine out in the colder air. The cold is causing the air pressure to drop several psi below the recommended level.

Pure nitrogen isn't as affected as air by changes in temperature, so that's why it appears to "fix the problem." But a simpler fix is to just put in more air!
 
"Pure nitrogen isn't as affected as air by changes in temperature, so that's why it appears to "fix the problem." But a simpler fix is to just put in more air!"

There is mis-information here. Air is 78% nitrogen and the remaining gases follow the same ideal gas law property.

Here is a thread that I feel intelligently dicusses the use of nitrogen in tires:


http://www.eng-tips.com/viewthread.cfm?qid=120996&page=1
 
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