Good morning I have a 2003 H2 the problem is my fuel gauge shows empty and low fuel light on when I fill up
when gauge shows full it’s empty

any suggestions

 

The fuel level sensor is essentially a variable resistor attached to a float located inside the fuel tank (see below)











Sounds like a break in the wiring, a faulty sender or a faulty PCM (Note an open-circuit will ready "Empty" )
Suggest the following:-

1. Unplug the 4-Way sender connector at the pump and place a 150Ω resistor between it's Pins B&C i.e. simulate the sender. With the ignition on, the fuel gauge should read about 1/2 full, if it does then your pump is most likely faulty, if not continue on below.
2. Inspect the 4-Way connector at the fuel pump, if possible disconnect it and measure the resistance across Pins B & C i.e. middle 2 pins on the pump's connector. I'm not 100% sure about an 03 pump, but an 05 measures 246.5Ω when empty and 40.5Ω when full (see graph) Access is likely very, very limited, so you could buy a pre-wired connector like this one and use it just to prove the sender works (note the eBay compatibility check says "doesn't fit" but it looks the same to me) this part is cheap compared to doing the job of replacing the pump etc.
3. Check the Splice S304 linking PCM connector pinsC1-23 to Fuel Pump connector Pin "C" located 21.5CM from Ground G300 "On Left Side of Body Mount in front of Driver Door"
4. Check the wiring going to PCM connector pins C1-23 (Low Ref) and C2-54 (Fuel Level Signal) With the battery disconnected you could unplug the PCM and measure between these 2 pins, you see between 50Ω and 250Ω depending on the fuel level. Never done this in practice, but it looks possible. If the reading seems sensible, it could be a faulty PCM i.e. it's not reading the sender.

These are theoretical checks based on the GM wiring diagrams and parts I have here.

Please let me know if it helps and if you sort it...