I recently bought a 2000 GMC 2500 4x4 crew cab 350 v8 old style. First the fuel gauge bounces at idle but gets better when driving almost steady moves very little but really fast? Is it a sensor or can i put a additive i fuel? Also my security dummy light just came on? Why and what can i do to fix?

 

I'm just throwing this out there because I drive a Chevy but I was reading on another forum where 99 and 2000 csilverados were having the same problem so GM most likely put the same fuel gauge in both trucks, someone suggested looking at the power and ground for corrosion. http://www.ringsurf.com/forum/answers-wacky_gas_gauge/ here is the post for you if You have not googl'ed it yet. Hope that helps