Gas Guge Question: Needle Bouncy; Bad Ground?

[TIMSPEED]

I think my Gas Gauge problem may lye in a bad ground connection. Tonight, I was driving around on a PERFECTLY smooth road, yet the needle was still bouncing. Also, when I was stopped at a red light, it was still bouncing. So, what wire should I check for continuity or what?
IIRC, the guage used in our trucks has only one wire going to the tank, and it's a ground wire, because the sensor in the tank is basically a resistor, when the tank is full, it reads 0ohm, when the tank is empty it reads 90ohm, right?