Check engine light help

My check engine light has been on for years but my truck as always run just fine so I never bothered with it. If I disconnect the negative battery terminal the lights goes off but It will come back on a few miles of driving after I put gas in the truck. I know I can get the diagnostics but shouldn't it be something with the gas cap vacuum? I always turn the cap unill it clicks a few times

 

When you get the diagnostic go to autozone. They will do it for free.

 

depends on the error code...

have autozone check it

gas cap seal could be bad... take a look at it, if the rubber is cracked at all replace it

 

YEARS?? Holy cow man...That's dedication to not seeking help.

You need to get the code read and go from there. It could be the gas cap but it could be 100's of other things too.

Have Autozone grab the code and then let us know what you find...

 

Well I had autozone do their diagnostics when it came on and it showed somethig about the gas cap and it's been inspected by toyota a time or 2 and they couldn't tell me what was wrong. It isn't effecting the trucks performance so I just ignored it
When I find out exactly what it is I'll post it