Well, maybe yours didn't have it. I was under the impression all Humvees had it, but it turns out that not all do...

This unique configuration of components along with military 37x12.5 radial tires with low-profile runflat devices allows the HMMWV to go places that no other wheeled vehicle in U.S. or foreign military service could go. Some HMMWVs are equipped with an optional central tire inflation system (CTIS). This enables the operator to adjust tire pressure from the driver's seat "on the move," to adapt to changing terrain conditions for greater off-road mobility.

The full story is at this link.

im in the army and i can tell you 99 percent of the m998s or its variants ("humvee") in the military do not have CTIS. its an option for civilians to baost about. the main vehicles in inventory with CTIS would be your larger vehicles like LMTVs and upgraded duece-n-a halfs and five-tons.

Alright im being a skeptic here, I just had the light come on for me. I know damn well i dont have those sensor thingies in my wheels, I bought 767 steelies... Im inclined to think it uses abs like karlan says. One of my muds was a little low, 27 and the rest are about 35... i just filled it so we will see how long it takes for the light to go out.

Damn, must keep you busy driving all of 'em.

Do you have an 05/06? Where did you get steel wheels to fit? The 05/06 uses sensors, I think we have already proved that.

Just a side note - my pressure sensor clicked on about a week ago. At the time I didn't have a pressure gauge in my Xterra (and for some reason, no place in NYC seems to seel them), so I stopped by a gas station and added a bit more air to each tire. The sensor didn't go off. When I final was able to get to an Autozone a week later to get a gauge - I found the front passenger tire at 80psi, and others at 60psi. (explains the bouncy, unstable ride I've been having lately).

Bottom line is that the sensor also seems to go off when you have too much pressure in the tires or there is a very unequal distribution of pressure between tires. It was odd, because I hadn't added any air since rolling off the dealer lot, but I guess temperature changes could have come into play.

60 or 80 psi are you sure?
I am certain that temperature did not play a roll in going from 35 psi to 60 or 80 psi.

Mine came on yesterday. All four tires (at 900 miles on the odometer) had 28-30 psi. I pumped them all up to 35 and the light went out in a quarter mile of driving.

The sensors will come on if one tire is a lot different than the others or if any one tire is below 28psi.

That would explain why at 80 and 60 psi the sensor went off.

How new if your X? I found when I got mine home from the dealer that the tires had about 55 psi in them. I let out a lot of air.

My light came on today on the way home from work. The left side tires had 32 p.s.i., right side had 33 p.s.i. I put 35 in all four, we'll see if the light goes off tomorrow!

I think the 60 to 80 psi came from my inflating the tires when I thought the light was on because the pressure was low. Once I got a gague and could accurately set the pressure to 35psi, the light went off. My X has 10,000 miles on it now, had it since March.

You have had the X since March, you put 10,000 miles on it and this was the first time you checked the pressure? Wow, hope your tires last.

Yeah, my bad assuming the dealer would actually check everything before I left the lot. I'm looking to put some BFGs on anyway, so I'm not overly concerned about the longevity of the stock tires.

Well, even if they were set at the dealer (which they never are), after 10K miles and 7 months, they should have been checked.

I check my tire pressure and oil every other fill-up which is about 2 weeks and/or 600 miles.

Yep, I was planning on rotating the tires and checking the pressure in each this weekend. Unfortunately, the pressure sensor kicked on a few weeks beforehand.

I was just sharing some first-hand experience showing that the pressure sensors are not only tripped when pressure is low...not looking for a lecture on my maintenance procedures.

Some place in the Owners Manual it talks about why if you change to the spare tire the low pressure light comes on. This is because the spare does not have the sensor. So it's there, just not as clear as the big bold letters on the cover of the Hitchhikers Guide to the Galaxy.

Hope this isn't true. Just rotated my tires and included the full-size spare, thinking it was smart and would stretch tire life. It doesn't make much sense to include a full-sized aluminum wheeled spare, and not include the sensor!

Pull out the owners manual. It's in there.

EDIT:

2005 Owners Manual
Section 6-2
LOW TIRE PRESSURE WARNING
SYSTEM
This vehicle is equipped with the low tire pressure
warning system. It monitors tire pressure of
all tires except the spare. When the tire pressure
monitoring system warning light is lit, one or more
of your tires is significantly under-inflated. If
equipped, the system also displays pressure of
all tires (except the spare tire) on the display
screen by sending a signal from a sensor that is
installed in each wheel. If the vehicle is being
driven with low tire pressure (lower than 28 psi,
193 kPa), the low tire pressure warning system
will activate and warn you of it by the low tire
pressure warning light. This system will activate
only when the vehicle is driven at speeds above
20 MPH (32 km/h). For more details, refer to
“Warning/indicator lights and audible reminders”
in the “Instruments and controls” section, “Tire
pressure information” in the “Display screen,
heater, air conditioner and audio systems” section
and “Low tire pressure warning system” in
the “Starting and driving” section.

Hmmm....I am willing to bet that the "SPARE" is the one not hooked to a hub, regardless of which of the five rims you have....

IE: Only the hubs connect the tire to the system, so the spare isn't on a hub...and isn't monitored. (When you rotate, the tire that goes from a hub to the spare position becomes the next unmonitored tire, etc...)



Easy way to tell, look at your spare next to one of the known working rims...the rims have a channel for this purpose...., the spare rim and the normally mounted rim should both have this feature.

Example of the other way: My wife's Mini Cooper has a little airline connection you screw onto the spare tire's valve stem before storage...the car monitors the spare's pressure via that connection.

I thought it was determined earlier that the system was wireless, using an RF signal?

The way you can tell, and someone said he already looked, is to see if the spare has a metal (aluminum) valve stem. If it's rubber there isn't a sensor on the other side of it.

This thread should be renamed a tad and stickyed.

Okay, my tire sensor alarm just went off this morning. Damn that's loud.

One tire was just 4-5psi below the others. 34,34,33,29.

I don't think it has a screw or any thing, but I did go off road yesterday for about 5 hours. I'll look at it at lunch.

After checking the tires and driving to work, I debated whether or not I like this new sensor. I decided it's okay. With out it, I might have driven on that tire (with or without screw in it) for a week before I would have checked it. With the sensor, I'm told I have a tire issue, I need to check out.

With that said 5 psi might be to small of a difference. Maybe 8 psi would work a lil better.

It's more likely not the change in the pressure between the tires, but that one was at 29psi. That is close enough to 28 psi that it probably tripped the sensor.

Also keep in mind that your gauge is likely off some. It might really be 28 PSI or lower.

How many times have you cruised down the road and noticed someone driving on a half flat tire? All too common a sight for me. I think this is good item, and I'm glad to have it onboard. Then again, mine hasn't gone off.

I too like the system, I check my pressure every 2 weeks or so and just this last Friday the light came on. After checked both my front tires were down around the 28psi mark. I blame this on the 15ºF temps that night.

I do wish it was hooked to an LCD display and actually tell you the pressure. From what I have read, the system has this ability.

Note to Nissan: see above. hehe, yep a dash display would kick ass. Use existing lcd display, and push button. Mark it: LF:34 RF:34 LR:33 RL:28