Air pressure gauge help

2009 w900. Just bought the truck knowing it needed some tlc. They had universal air pressure gauges in dash so I was expecting someone didn't want to buy the expensive oem gauges. Got the dash open and both factory gauges were laying inside. Both gauges are pegged on 150psi. Tried switching the pressure sensors around and still the same. I highly doubt that both gauges and/or both sensors are both bad at the same time. Anyway to diagnose this or throw the parts canon at it? Maybe the cab control module? Any help is appreciated. Thanks