if it truly doesn't work then it's warranty.
but - it is a monitor, not a gauge, and meant to tell you that you might have to check your pressures. with a gauge.
that aside, pressures will increase with sunshine, higher ambient air temps, and time driving. the harder you drive the more they will increase BUT
if you have factored all of that in, my experience says that if THROUGH DRIVING, your pressures increase by more than 10%, you started out with not enough air, if less than 10% your starting pressures were too high.
others may disagree with me on this, I don't care.
the monitors do a good job of telling me I'm within these parameters.