1999 Chevrolet Tahoe Q&A
1999 Chevrolet Tahoe Question: what to look for when po440 evap ctrl systems malfunction code comes on
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. - milesauto
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. - Hal...