I found mine out the hard way and had to look into it (and then read the F-in manual to confirm it existed) ..
LOL
We had a few below-freezing nights, so I pulled into work before we opened and I had the rig running and grabbed my tire inflator. After a bit (as I was watching the gauge) it was like the truck alarm was going off .. or it was reading the gauge along with me .. HONK ..
OK .. weird ..
next tire ..
HONK ..
WTH!??
Master Tech came over and was like, "yeah it is telling you that your are at the proper pressure and you can stop filling." I was like, "BS DUDE BS - what is wrong" LOL
Perfect Idea if you ever have to stop at a Quik Filler-Up'r and they don't have a gauge, just the filler hose .. Nicely done, FCA .. nicely done!