My low pressure light is on. The pressures were checked with an analog pressure gauge and are all 35, even the spare.

 

FYI it only reads 4 tires, the ones rolling on the ground It doesn't read the spare.

Did you try increasing the pressure above 36? Put them at 38psi and see if the problem goes away?

 

Are you taking it for a drive? I think they need to be rotating for a bit to send a reading.

 

On my '13 they don't need to be moving at all, unless something changed along the way.

 

They did change several times over the last 6-7 years. I have a 2012. I think they need to spin to send signal. That's why the spare doesn't show up, even if it's completely flat. In 2012, the display does not read actual pressures, only tells you if a tire is low and does not tell you which one. Later years actually give you digital pressure numbers for each tire.
My 2012 low pressure light doesn't come on until around 33psi but I have read others needed to be 38 or higher.

 

You are checking the tires absolutely cold pressure yeah? If not let them sit over night and do a check first thing in the morning. Had a Nissan that was very touchy about cold versus moving pressure. Let it sit out overnight serviced to specs, problem gone.

 

Y, that change must have happened going in to '13, cuz mine shows the pressures for each individual tire on the display. So many people remove the TPMS all together when changing wheels, but I've always found this to be extremely helpful.

Sometimes you have to go up over the threshold a bit and then come back down. If the threshold is 35 and you're right at 35....you might need to add a bit more to each to reset things, then bring em back down to where you want. It's at least free to try.

 

FWIW there are two different displays available even in 2017 JKs ... the one I have shows individual tire pressure but the other one is more of an old-school LED display with far less detailed information. IDK which package is which but when I rented Jeeps in HI in October they were both 2017 models and they both had the limited LED display and not the MFI like my '15 JKU has with all kinds of stuff like oil pressure and individual tire pressure and all that jazz... no buttons even to navigate through such menus.

BTW the way the TMPS works in a JK (well, a '15 anyway) is there are three sensors, and each sensor can read all five tire monitors including the spare. It only reports on four, and it identifies which is which due to proximity to the sensors. IIRC there are two sensors in front and one in the rear. The tires have to turn on the ground in order to turn on the sensors, which preserves the battery in each sensor (since it's not replaceable). They will stay on and keep transmitting for some time after the tire has stopped spinning, but IDK how long that is. Hours? Long enough that the tech at Discount Tire can use a gizmo to verify each sensor is working while the vehicle is parked. The spare's sensor will continue transmitting for a while if you do a 5-wheel rotation once you mount a formerly on-the-road wheel on the tire carrier, but as soon as you drive it the formerly-spare tire sensor will start transmitting and within about 10 miles the Jeep will work out which wheel is in which spot, but up until that time it may erroneously read the spare's pressure and "think" all the tires are still where they used to be. Eventually it'll rule out the spare and stop reporting it, and then some time later the spare will stop transmitting.

Anyway, if your "low pressure light" is on, that's the TPMS indicator that kind of looks like a horseshoe, an orange/amber light in the dash, right? That indicates either low pressure or one or more sensors is failing to transmit. If you are certain all tires are above the threshold (put them at 38 psi to be sure) then go to a Discount Tire shop and they will be able to test each individual wheel sensor and ensure it's working, likely they will find a dead sensor.

BTW if you do wind up doing this and find a bad sensor, you can buy 4 sensors on Amazon for the price that Discount Tire will charge you for just one, but it's very hard to find a shop that will replace a single sensor that you bring them for a reasonable price and in the end it may be nearly as cheap and a lot easier to just pay the $70 or whatever for Discount Tire's sensor costs since they will install it for free right there while you are waiting, right when they just told you which one is bad. I'm an uber cheapskate but I think I'd save myself the hassle in the future.

And another BTW, those Amazon tire pressure monitors have an alarmingly high failure rate. I've had two DOAs out of 7 I have bought. One was replaced by the vendor for free but of course I had to pay to have the bad one swapped out, and the other one I didn't discover was bad until it was too late to return so I bought another one for like $12.

 

I've never heard this explanation, and now it makes perfect sense why it works so well for how I use it.....mainly for airing up/down when wheelin. That battery is still active so it's working even though the jeep is stationary. I'd presume starting after sitting overnight, if tried changing that pressure it's not going to be picked up till just a bit down the road. Thanks for the thorough explanation!

 

Yeah that's a nice feature of the JK TMPS to give you an indication of tire pressure when you air up/down in situ. I know all the "old way is better" guys think the solution is to somehow disable TPMS and throw that electronic junk in the trash but it really is a useful tool if you embrace it It's also a frustrating thing that'll drive you mad when it's not working correctly... try having a bad sensor on your spare then trying to chase it down after you do a tire rotation is a big pain; that's why I had to learn all this stuff

I presume so as well, but I am not 100% sure. Actually I suspect the TPMS system in the Jeep (not the wheel sensors) stores last-known data and doesn't report a low tire/failure/etc. until it can read the new values. So I think if you were to have the tires at like 15 psi then shut the Jeep off, re-air the tires to 38 psi and let it sit overnight, when you start it in the morning it'd still read 15psi until you start driving and the wheel sensors wake up and begin transmitting.

BTW the 10 miles down the road thing is just for sorting out which sensors are on which corner of the vehicle. It will read new pressure values very quickly once you start driving or the wheel starts turning. So like if you did your overnight reinflate thing, it might pick up the new pressure as you back out of your driveway. But if you also were to have rotated the tires while the Jeep was off, then it would report the wrong pressure for each corner for some time, like 10 miles or so, and if you don't drive far enough it might be a while before it sorts it out.

BTW there's a logical oddity that happens if you rotate in a tire with a bad or missing sensor. Say you do a 5-tire rotation, and your spare has a dead sensor (as I did). What will happen is for a little while after you do the rotation, the spare will continue to transmit and you will get four tire readings that look right; the spare is still transmitting. The Jeep won't try to sort out which tires are on which corner because it doesn't detect anything changed. All four tires are still transmitting, it has the values it needs, it doesn't think anything is amiss. Once the spare stops transmitting then you will get one corner showing "--" and a TPMS warning light, which is trying to tell you that you only have three tires transmitting. However, it will still think the other three tires are mounted where they were before you rotated tires, which will be extremely confusing. So if your front-left tire moved to the spare, then it'll show "--" for the front left tire. But of course, the formerly rear right tire is mounted on the front left and that sensor is working fine. It's just that the Jeep thinks that tire is still mounted on the rear right. Again, no new sensor has been introduced to cause it to recalculate the tire locations. The actual dead sensor is whatever one was formerly your spare, which in my case was on the rear right. The TPMS will remain confused about the location of the tires until you repair the bad sensor. Once you do that then suddenly it has a new signal on the rear axle and this triggers the recalculation, which takes about 10 miles.

Anyway, just posting that here for completeness of information, in case someone searches later. Maybe the OP can rename the thread to "TPMS" instead of "Tons" ... guessing autocorrect made this happen. Or maybe an admin can merge this thread with the other one and fix the title.

BTW this information about how the FCA TPMS works in a JK (and also in several other FCA vehicles) was not easy to find or work out. If you have a bad sensor mixed in, it really can be very, very challenging to determine which one is bad. The TPMS is not your friend in figuring it out, since the display will show you likely-wrong information about which tire sensor is bad. You need the gizmo they have at tire shops to detect which sensor is not transmitting. Fortunately Discount Tire will check this for you for free and usually you just have to pull up and ask, no waiting, etc., and those shops are all over the US. Alternately you can intentionally set the pressure to different values per corner and then find which one is bad... say you set LR to 15psi, RR to 20psi, LF to 25psi and RF to 30psi, then you can find the bad sensor by determining which of the four pressure values is not being reported. It's a pain but at least you can do it yourself. But you probably can't pop and re-seat the tire bead yourself so I say just go to a tire shop and hand over the Visa card.