Hi there and welcome Mitch
Did you add any new electrical devices to your Truck around the time this problem occurred?
ok, disconnect the power to the stereo and any electrical devices apart from the GPS units, then test if they now work.
There is interference on this so we need to eliminate what this is.
ok, I will mark this question to remain open if you have further issues, but it will be electrical interference thats causing this, unless you insulated or did something to the cab, this is the only cause. May be an issue in the engine with a solenoid or other component causing this but it will b something electrical.
ok, they can contact me via this web page, on your account this comes direct to me.
But if it did work and nothing changed, then it has to be electrical interference for this.