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<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by usetosellhummer:
they are not required and they suck. disable them! get a tech to do it </div></BLOCKQUOTE>

They may suck, but you don't know the law, so why act like you do? The Federal Regulation is FMVSS (Federal Motor Vehicle Safety Standard) 138 - Tire Pressure Monitoring System.

FMVSS 138 requires that a phase-in period for tire pressure monitoring systems is as follows: 20% of all new cars must comply by Sept. 1 of 2005, 70% by Sept. 1, 2006 and 100% by Sept.1 of 2007

Therefore, GM (as I believe all manufacturers) will install the system on all new launched vehicles; as is the H3.
So, yes they are required, but not they didn't have to be on the H3, it only made sense to GM do design them in from the start.

As to sensitivity, I believe the spec is 25% variance from the tire pressure noted on the tire pressure placard. For the H3, this is 35 psi so if the sensors drop below 27 psi the system will activate.

I highly doubt if any tech will disable them, since it would be considered a violation of Federal law. In addition, I don't believe there is a way to disable them via a Tech 2. Probably have to have a complete different calibration.

Let's also take into consideration how many of these sensors are out there on many cars. GM does not manufacture these sensors, and the companies that do are selling to other manufacturers. This forum is small majority of the H3s sold, so ten or twelve people on this forum complaining does not constitute a large problem.

The largest problem due to the warning, as recorded by engineering is simply the customer does not have the correct air pressure in the tires. On an H3 it is supposed to be 35 psi, and checked when COLD, not HOT.. Therefore, if the tires are set correctly, and the vehicle is parked on a day when it is 85 degrees, and that night it drops to 45, the tires will register approximately 31 psi. This should not be enough to set off the system; however, if the tires are set at 31 psi cold, and they drop 4 psi overnight, then yes, the system may activate.

The reason for this regulation is the general population has no idea about checking air pressures in the tires. Most believe that the oil change shop once every three months is good enough. Problem with the oil change shop is that many adjust the tire pressures according to the label on the door, but the tires are hot. So, pull in your Hummer with hot tires, the guy checks the placard and sees 35 psi, adjusts your tire pressure to 35 psi, and when the tire cools it will lose 3 or 4 psi. Now the ignorant person is driving around and in a few months the ambient temps start to drop. Well, one morning said customer starts his vehicle and the system tell him he is low on air. Off to the dealer he goes, and the dealer has to give him a quick description on how to check tire pressures.

I have known people for years who have had these sensors in their Vettes, I have had them for years, and it seems only on this forum is there that many complaints. Now, I'm not saying there are not bad sensors out there (I had one on my '03 Vette), and I'm certainly not saying people on this forum do not know how to check their tire pressures. People who visit forums like this are usually pretty darn good car/truck people, but the regulations were made for people out there (and they are the majority) who have no idea that tires have air inside them.

Just remember, for any vehicle you own, and if they have sensors, read the recommended inflation pressure on the tire placard, and go with that recommendation, and make sure the tires are COLD (at ambient temperature). Also, understand, they will lose pressure as temps drop, and sometimes air will leak through an aluminum wheel due to porosity of the wheels.