Gas tank builds high pressure between fill ups and check engine light is on on 1999 GMC Safari

code P0440 evaporitive fule system do I have a blocked line a bad canister or a bad purge selonoid ?

can I fix or do I need a Mechanic?

Asked by for the 1999 GMC Safari
2 answers
P0440 is a general EVAP system code. There are many posibilities. I would recommend bringing it in for diagnostics to find out precisely where the fault is. We can smoke the system to check for leaks as well as other test to see if your solenoids are working properly.
get it scan for codes, bring it to autozone