Gallery pressure

Theres only one pressure sensor in the whole system and that's the one located on the valve block at the compressor. When the gallery pressure is low the ECU opens the valve (its in the main valve block attached to the compressor) to the reservoir under the passenger side (NA) sill and runs until the pressure reaches the shutoff value of 255 psi. Then the valve block closes the valve from the block to the reservoir tank, assuming the ride height does not need to be increased further.

The pressure sensor monitors the "gallery" which is all the plastic piping from the compressor block to the front and rear valve blocks, and back thru the compressor to the exhaust valve. The dessicant tank on the compressor acts as a small volume of compressed air, probably larger than all the internal capacity of the tubing running between the various valve blocks.

When the ECU calls for some automatic leveling and the engine isn't running the valve to the reservoir in the main block will remain closed, and the exhaust valve at the compressor will open, as will the valves in the front or rear valve blocks (under the truck on the right front firewall and up under the right rear wheel well liner) to lower the higher side, or the entire front or rear of the vehicle. The exhaust valve at the compressor is supposed to be the only way to reduce air pressure in the gallery, and or the reservoir (excluding leaks).

Auto leveling doesn't raise the suspension height when the vehicle is off, leveling is always in the downward direction, it will never raise the height of the truck, or one side or the other until the key is in Position 2 (RUN). It will lower the high side down to match the lower side, or end of the truck, which is how these trucks end up on the stops. The compressor will not run unless the key is in Position 2 (RUN). If the truck is running, as soon as pressure in the "gallery" drops below about 200 PSI the compressor will start and recharge the "gallery and reservoir back up to 250 PSI.

So you need to check your plastic lines and fittings from the compressor block all the way to the front and rear valve blocks, as well as the exhaust valve and the seal on the dessicant case head and the line back to the compressor from the main valve block for leaks. Pulling the fuse to the ECU is preventing any of the various valve blocks from being energized so the air springs can't level the truck out. In addition to a very small leak in the "gallery" somewhere, You may still have an air spring leaking, but since the valve blocks can't open, the truck won't auto level and end up on the bump stops.