Checked cap.. cap is good.
Try replacing gas cap with a new one.
Then the trouble code should have indicated a EVAP emissions slow leak. These are hard to find, what is done is a smoke test in the EVAP system to find the leak. You would have to take it into a shop that does the smoke test to find the leak,
Good morning Bob, bright and cheery today I see...
It's more than likely your evap emission system solenoid the same thing happened to my buick lasabre. If you tried the gas cap already it's thst solenoid the sensor is on yur evap canister
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