Just got a 98 Trans am and fuel gauge doesn't work. When car is off, it reads at 1/4 tank. When car is on it just stays on empty. Would this be a sending unit issue or possibly something else?

 

When off, the gauge can "float". When on, it indicates the level, when working right. Sounds like a bad sending unit.

 

Aight, i will check and see if there is a trap door to get to fuel pump. If not, i guess i will be doing math for a while lol.

 

Yeah, I don't know any diagnostic procedure to narrow it down for sure. Maybe someone more knowledgeable might chime in here to add to this.

 

There's a plug in front of the driver side rear wheel where the wires for the pump go through. You should be able to unplug that and short the gauge wire (purple if I remember) and un short to see if the gauge moves. Double check on wiring diagram though.


I found it - circuit 30. shorting and open should flip between empty and full.

 

What do you mean by short the wire? Im not to technical with electric stuff lol

 

Short it to ground - body structure. That side of the circuit measures resistance across it and it uses a ground side to do it. So if you short it to ground - you'll get 0 resistance, leaving it open is infinite resistance. You should be able to have a helper let you know if the gauge is bouncing when you do that (key on, engine off). if so, the problem lies between there and the sender. If not, the problem lies between that plug and the pcm.

 

Ah ok gotcha. I will try that one day this week.