The fuel gauge on my '92 jeep wrangler is stuck on empty. i'm getting a voltage reading of 9 volts at the gauge on the wire coming from the tank it runs fine otherwise so it's not a connector

You will need to test a number of things, the fuel gauge is part of a rather simple circuit.

Battery -> gauge -> tank sensor -> chassis ground to battery

If the circuit is broken at any of the steps, your gauge will read "empty". If the tank sensor is bad, it could read empty, or if the float in the tank has sunk, it will read empty.

I start at the gauge with a "test light" that glows when it sees battery voltage. Get a light at the connection to the gauge? Good. find the sensor connection, usually on top of the tank, accessible in the trunk. Probe with test light. Light on? Good. Connect wire to ground, gauge should read "full". If all that is as I said, then the tank sensor is bad. If you don't read battery at any step, you know where the problem is.

nothing wrong with the ECM unless it has the voltage regulator as part of the system
indicates faulty wiring and faulty alternator
have a load test done on the battery
have an auto electrician do a full charging system check
charging voltage should be 14.5-14.8 volts DC
battery voltage should be 12-13.5 volts dropping to 11 volts when cranking the engine
make sure that the drive belt tension is correct and the belt is in good condition

Sending unit which now comes with a fuel pump

Bad fuel sender unit or fuel sender wiring

When testing a fuel guage you should disconnect the wires to it,guage should read over full,ground the float wire,turn off key then turn back on should read empty.You have to cycle the key for guage to move.If still inop the wire is broken in the harness between the tank and the dash.Voltage on the float wire is low.When tested with a test light it will barely light the light and pulsate.This test indicates the wiring is good.

If your checking fuel pump voltage, check other wires while cranking that will be fuel pump voltage and will only have voltage while cranking, or 3 to 5 secon after stop cranking. the one 5 volts will be gas gauge.

you have to take it out of the gas tank to check it.

Two possible problems.... the temp gauge wire is a single green wire attatched to the driver's side head (no1 bank) near the front in the side (in front of plug #1) ground it and your gauge should go to full hot,,, same with the fuel gauge, if you unplug it at the tank it should go to empty, or visa versa... if the gauges respond, replace the sending units, if they don't, replave the instrument panel

p0463 is a self diagnostic code that is for the fuel gage sending unit located inside the fuel tank if your fuel gage is reading empty just after you filled it then that verify's the code is correct you have a bad sending unit

You can usually only get about 18 gallons in a 19 gallon tank and you likely have 4 gallons left in it when the gauge reads empty