If you have the Silverleaf monitor, the Smart Tire readout should be on the lower right corner of your screen unless you've selected video to turn on the rear camera. That will cover up your smart tire readout. The sensors are inside the tires strapped to the wheels. The receiver is under the dash.
As far as the remote you suspect is for the awning... it could either be for the awning or for the Drain Master drain hose to extend and retract it. Does it say Weather Pro on the remote? Do you have an awning over the entry door as well?
If this is indeed the awning remote, perhaps the receiver has been switched off. Check the ceiling above the passenger side storage bay nearest the front wheel.
The fuel/water separator can be accessed by opening the battery bay door and then open the service panel door. You can find your oil and trans dipsticks there and the air cleaner. Next to the bulkhead you will find the filter you seek with a petcock at the bottom for draining off water if there is any. Remember not to completely drain the filter or you will regret having done so.
Janet and Todd Legg
2006 Alpine Apex M-40FDQS #75594
2014 Honda CRV w/navi