To diagnose that problem your going to need a smoke/nitrogen cart possibly a ultra sonic leak detector and a tech2 with the correct software to start.Also the knowledge to use all that stuff your best bet would be to take it in somewhere those tool's are very expensive.Otherwise there is no way of telling if you have a leak somewhere or a bad sensor wiring etc.

Answered by saturntech9 (expert)
23,174 answers provided

Depending on which engine you have i have seen some canister purge solenoid's stuck open all the time causing that code.The one on the driver's side facing the engine right by the valve cover.It should be closed with the key off and engine cold.If you can blow thru it with the hose's off it it's stuck open.

Answered by saturntech9 (expert)
23,174 answers provided