I have an 07, 2.7. 7800 miles. TPMS acts up once or twice a month, I have yet to have a low pressure reading with the gauge. Generally its off about 4 lbs various tires and sometimes shows --- (zero). First service is due in October. I'll live with it till then. In the mean time the problem seems to correct on its own in a few miles.

Dito in my '07 S. I have the same problem with my right rear, but it happens less if I drive the car everyday, like now during our good Portland, Oregon weather. When my car sits during the winter and spring and is only driven two or three times a month or less, the system alarms me everytime.

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Mike "Big Daddy CS"
'07 GT Silver

I started getting these errors yesterday. First it was -4 in the front right, then it went away and now -4 on the left rear. I checked the pressures and they are the same on the front and same on the rear.

If this keeps up I am going to take the car in. I know the tires are fine but the alarm on the dash is annoying and my wife thinks the car has a problem.

I have also noted errors in the static pressures, always low, but I have also noted that the system seems to be much more accurate in the "info pressure" mode (difference from reference corrected for temp). In my car at least, this display is in close agreement with my manual pressure gauge. Looking at the static pressure measures, variation in temperature is the biggest contributor. Atmospheric pressure varies only a couple of percent due to meterological effects (no more than about 1 psi out of 36 psi for all but the most unusual conditions). Similarly, altitude causes a small error, 1 percent at about 1200 ft msl and 2 percent at about 6000 ft msl (about 0.5 psi out of 36 psi in Denver), or 1 psi in atmosphereic preasure for 2,000 feet of altitude change and 2 psi for a little over 4,000 feet of altitude. Temperature is the biggest variable, causing a little less than a 1% variation for every 10 degree F change from standard (68 deg f). The interesting thing is that every complaint that I have read indicate that the readings are low. If it were random sensor error, there should be high readings as well as low. Now I don't know about everybody else, but I am much more likely to check my tire temp in nice weather than cold. If it is 78 deg F and you fill the tire to placard pressure, you will be filling it approx 1 psi low. So maybe we are inducing our own errors. This winter I will watch my pressures and see what happens below standard temperature. This summer I copied the pressure vs temp chart out of the owner manual, TPMS section (page 109 in my book), inflated the tires to chart pressure corresponding with temperature ( the chart is for the rear tire and based at 36 psi, so for the front, I would add the same delta to 32 [placard pressure for the front]) and had no false warnings.

With the observed accuracy of the info pressure, I can only assume that the in-tire sensor also fairly accurately measures internal air temperature. I have checked the manual pressure gauge reading with the info pressure delta at several temperatures from the 60s to the 90s and at the track in 94 deg F ambient and it seems to be better corrected than the static readings. I just can't figure out why it only works with the vehicle motionless.

Has anyone else seen higher agreement between the info pressure delta pressure measurement and manual gauge readings?

Lastly, the system probably saved me at least a rim when it detected pressure loss in a rear tire due to a large nail. I like to think that I would heve noticed, but I am very happy that it warned me.