low air pressure alarm fleetwood excursion

I recently purchased a 2003 fleetwood excursion , diesel 39P . My problem is the low pressure alarm is on continuously and the front and rear air pressure gauges both read "0", however the brakes work perfectly fine and the airbags fill fine.

Initially it appeared as it was just a gauge issue as one gauge showed 130 and the other showed 0. After 3 new gauges exchanged back and forth it is apparent the gauge reading 130 was the dysfunctional gauge. Replaced gauges with new and both read "0".

It seems that whatever sends the info to the gauges is not working. ????

Any ideas would be greatly appreciated. Thank you.

Randy