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Q: what to look for when po440 evap ctrl systems malfunction code comes on on 1999 Chevrolet Tahoe

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
will not pass smog test.I have changed o2 sonsors in exhaust system.
No car image 94a1663db56199c5353592009e34aaa51078a2469bed068bb8d6f0ba43accf97
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We just use a smoke machine to find leaks in the evap system if the problem is not a solenoid. Check your gas cap first though.
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Other than checking gas cap to make sure its tight and its seal is not worn out that's all one can check without getting into evaporative test. In my opinion evaporative leaks are the most challenging to diagnose. I am not in CA. so I do not know Smog rules there...but my guess it will not pass. I suggest you take it to a professional that is equipped and has knowledge to repair your problem.
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