EVAP Code and misreading fuel gauge

[thdrill]

Recently I have been getting an EVAP code (believe it is P0455), which I thought was resolved with changing out the fuel cap. Now I remain with an intermittent code and have noted that my fuel gauge reads accurate at startup and drops down to read 1/8th lower than actual. Any ideas if there is one thing that could cause both problems?

Paul

 

[Ojustracing]

Its possible, but I dont feel an 1/8 lower would cause a check engine light.

John

 

[thdrill]

I don't believe that being 1/8th lower than actual will cause a code either, my question is there a sending unit or something similar that could cause an intermittent P0455 code and have the fuel gauge read 1/8th lower than actual?

 

[Ojustracing]

Paul the code is for a large evap leak if I rememebr correctly. The sensors for the evap control and fuel gauge are not one in the same. Gm's do have a issue with the vent solenoid at the back of the truck going bad, i just dont know if the tahoe use the same piece. Also I have had a bunch of the chevy also with innaccurate gauges. Normally this is issue with the wiper contacts on the Fuel level sending unit in the tank. The sulfur componds in todays fuel cause wear and enventual failure of the piece.

Gm does have a newer fuel additive that is suppposed to help with this issue but I have never used to stuff. I would like to be able to give you more info but I cannot acces my work info from home.

John

 

[RIMZ24]

Any Ideas?

I have a 2005 Tahoe, with the same problem. P0455, and inaccurate fuel gauge. I was driving and it said tighten fuel cap after the check engine light came on. I tightened the fuel cap, light stays on. Took it to autozone to check the code and got the P0455. The print out they gave me says EVAP large leak detected.
Explanation. The ECM has detected a large leak in the EVAP system during a system monitor test. Probable Causes- 1- Defective loose or missing fuel cap. 2-EVAP canister broke, hose cracked or not connected. 3- Purge or vent solenoid defective. 4- Vacuum leak at engine.
Replaced fuel cap, no results. Any Ideas where to start??