fuel guage on e. low fuel light on. check engine light on. can't get tags. dealer charges $100 bucks for diagnostics. 3.5 hours later says " codes indicate high input on low fuel sensor.states that the 5 volt reference is at 6 volts? then says he has seen this before and the older the pump gets the hotter the wiring gets and that they must be shorted together. so i should have the pump replaced" i get the delphi pump @ $400 bucks install my self with a friend, put 8 gallons of gas in and the problem is the same. help.

 

bad fuel sender, it was never the pump at fault

 

before going to the dealer i cut into wiring harness along frame and used an ohm meter to watch the variable resitor's value change as fuel was poured into the tank. change in value was correct. all that i consulted said to replace the entire unit pump & sending unit due to probability of doing the other later. i don't feel as either one was the root cause of the high input on low fuel sensor. went to the dealer again this morning. the mechanic john is on vacation till monday and they would prefer that he were to look into the again. i paid for a diagnostic test but, i bet they want to charge me again.

 

You haven't stated the year of the truck so I'll go out on a limb and mention that the same symptoms occur on the late 90's early 2000 Corvettes. Using a 20oz bottle of Techron fixes the problem. I recall a couple of causes from poor quality gas to running on empty. Maybe someone else has more details.

 

before changing the pump and sending unit i put a can of seafoam per full tank on two tanks. the dealer stated chevy extended the warranty of inst. cluster to 80k miles for some year models mine 2005 included. my problem developed at 90k +. they ruled out the cluster, but never said how they checked so i don't know.thanks for the input. going to miracle worker @ helen keller chevrolet tommorrow.