2003 Check Engine Light

[arnoldw]

2003 check engine light is on. Have the code read says we need a new gas cap or have a leak of some sorts. Change gas cap light still on. Cannot at this time find the leak. The light my wife says goes off when we have more than a half a tank of gas and comes one when it goes below a half a tank.

It appears according to the gauges that when the light is off we get great fuel mileage but with the light on the mileage is in the tank.

Thanks in advance for any thoughts

 

[Prospect62]

Stupid question but did you have the code CLEARED after you replaced the gas cap?

I assume its a P0442, small evap leak? If that's the case it could be any number of rubber vapor lines to/from the gas tank that are leaking. Hopefully someone who has owned a Tahoe longer than me will chime in here and point you to a common leak area.

It may not be the gas cap at all, obviously. With less fuel in the tank, there are more vapors in there, which would be why the CEL seems to come on more with the tank emptier.