It sounds like his CTIS is doing the same as mine.
Today I checked the tank pressure switch and when the gauges read 120psi the switch is closed.
I removed the front QRV and with the truck running and CTIS on "HWY" there is no air coming out of the feed hose. There is also no air coming out of the lines going to the wheels/hubs. I would think that the controller should send a pulse of air every 5? minutes?
I got sidetracked with a fan clutch air leak so other than putting dielectric grease on the pressure switch and CTIS controller, I didn't get any further.
The gauges for the dry tanks can be misleading because they do not indicate the pressure in the wet tank (where CTIS air comes from). Such conditions as too-low idle, leaks past the Over Pressure Valve (which comes off the wet tank) or a leaking OPV itself can drop wet tank pressure without any indicator.
Your measurement of the switch closure IS a good test though, and high-enough pressure is indicated in the wet tank. But there's another 'gotya'. If the OPV is set at a high enough pressure it can fail to open even if the wet tank switch says "ok". If the OPV leaks it can also fail to pressurize the CTIS. So the pressure out of the OPV is something to check. Without pressure out of the OPV the CTIS controller has no pressure to work with even if the pressure switch is closed (like yours is).
The CTIS only checks pressure every 15 minutes and that can seem like a long wait.
BTW, the fan's clutch control pressure is also reliant on the OPV so if your fan is on all the time, that's a good diagnostic tool.