I don't know about Rangers, but on my mom's Mazda 3, as soon as the tires are the same pressure it goes off by it's self. Of course, you have to drive it a little bit for it to turn off though. They use the ABS sensors to see how fast each tire is turning and if one tire turns slower for an extended period (a low tire is smaller) it says a tire is low. So, if they are all at the same pressure, and you drive it around for a minute or so, it should go out on it's own.
Sorry for the explination but I figured I'd tell you how it works too.