The low fuel message kept appearing and the gas gauge reading empty when I knew I had gas, so I knew the sending unit was going, and there seemed to be a louder noise than usual coming from under the truck, so I took it in to the dealer for an inspection. Turns out there are two gas tanks, the main and a reserve, both containing a fuel pump and sending unit. It was the pump in the reserve tank that was making all the noise and that unit as well acting up, so I had the two replaced. The service advisor couldn't tell me though just what the layout of the tanks are. My manual lists the fuel capacity of my truck at 38.5 gallons but if I gas up when the low fuel light comes on, I can't squeeze 38 gallons in. So how big is the reserve tank? And when the low fuel light comes on, do I have a full reserve? I knew that when the light came on in my Jeep TJ, I had 3 gallons left in the tank. It's good info to know!