Just got my MaxiTPMS TS508 and it is supposed to have the ability to change the tire pressure placard values, but I am not seeing that option. Vehicle is a 2018 Toyota 4Runner.
Just for the heck of it , I wonder if you have a vehicle with different Tires that require a higher or lower psi than factory, if you could take the steel spare wheel and drill 3 extra valve stem holes in it and just mount the four TPMS sensors on the steel spare wheel and see whether or not the system is able to read them all or not.