Riversub

First time MB owner here and not sure if this is par for the course but the pressure in my tires seem to vary by 2-3 PSI frequently, which sets the warning light on. It is fairly inconsistent - if you take just one tire, for example, one day it will read 34 PSI, the next day 31, next day 33, then possible back to 34 PSI again eventually. Sometimes it fluctuates multiple times per day by 2 PSI which seems to trigger the alert.

I've reset the warning light, recalibrated the warning system and then it will be fine for a week or so but then go back to the behavior above.

30-40 degree temperature fluctuations are not uncommon where I live right now and I didn't have this problem over the summer where it is more mild.

No other diagnostic problems or warnings and I have had the car in recently for a 10k service.

In any case, is this type of behavior typical of the tire pressure warning system? It just seems a slight variance in the PSI will trigger the alert.

thefisch

my readings do vary like you stated. reading in the morning just getting out the driveway will be at 33F/35-36R and rise by 1-3 psi as tires warm up depending on how much driving I do that trip. I reset the warning system through the dash cluster menu when the morning reading is at the right levels for my taste.

I have seen two types warnings from the system. When it first got colder and my tires were reading about 30 or so, the car would say check tire pressure on the dash cluster when I turned off my car, kind of like a gentle reminder. Press ok and it goes away. Seemed to come on when the car would read 3psi/10% lower than the level I set.

The second type of warning looked the same except it was red and stayed on. It was when a tire with a nail in it dropped in pressure to 26 or so. Figured that warning comes on after about a 25% loss when it's time to take immediate action.

Mine is a 2011 so your newer version may act differently. Since you're under warranty, get the dealer to check it out if you think it's buggy.

mleskovar

The TPWS threshold for tripping a warning is always lower than what you set it at. If you set the TPWS after driving when the tires are hot you reduce the threshold. Ambient air temperature also plays into the TPWS. If you set the tire temperature when it's 50 degrees outside and it drops down to 0 degrees when you start driving the car later you will have a 5 degree difference in air pressure and probably trip the TPWS system. Fill your tires and set the TPWS system when it is as cold as it's going to be during drive time to solve your problem.

Live Oak

Deflategate!