Model number appears incorrect. Should that be LA5400XTW0? That's an old one (1988). First, check the water valves by simply unplugging the washer while it's filling. If the water shuts off completely, the valves are ok. Next, you will need to check the water level control. You need to remove the cabinet and check the air dome and hose on the lower right side of the tub. Pull the hose off the air chamber and check both for gunk buildup and clean out if necessary. Start filling washer with air hose removed from air chamber and blow into hose to activate the water level switch. If the water shuts off, the switch appears ok. You should hear a click in the switch. If the switch appears to be working and the air chamber and hose are clear of gunk, the hose may have a split or hole in it somewhere. If the switch is faulty, it is no longer available from APP but may be available elsewhere and/or as a used part. Search on part number 63835.

Eric