Root: catching up here and had a thought. Where do you store your RV? Ultimately found the cause of our 'check engine' as vacuum leak caused by rodent(s) chewing on the line from gas tank to generator. Not enough to spot a leak on the ground, but definately enough to blow gas on poor technician when he put the system under pressure. Any incriminating signs under the hood? (grass nesting materials, droppings, etc.) Good luck.
2007 Fleetwood Southwind 32V w/Ford V10