Gas gauge don't read right its always saying low fuel. Sending unit or gas cap

sending unit float/switch is bad.the whole unit will need to be replaced to correct the problem.or just keep the tank full and use the odometer trip button to keep up with the miles you get per tank,so you WON'T run out of gas again.if you get 350 miles per tank,go fill up,reset trip to ZERO,when you put 300 miles on it,go fill up and reset trip to ZERO,etc.the assembly is around $300.00,if you buy it and do it yourself.tank has to be removed to do this.if you decide to replace it,depending on where you buy it,some may ask if it's a 2 door or 4 door model.