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I have been trying to correct this for a year. I have the Autoenginuty Scan too with the GM enhanced feature installed but really not sure what I am looking at. I have replaced Gas Cap, Purge Solenoid, Vent Solenoid, and Tank Pressure Sensor. Can anyone help me Diagnose this system correctly I/E leak down test on vacuume on the tank? Thanks for your help.
P0442 is usually a small vacuum leak in the evap system. With Chevy most times its the gas cap or purge valve… if you have replaced the valve, did you test it before installing? Many times new purge valves are defective. If you do not test it, you will believe its OK and it still may be the problem. Recheck the purge valve. Hook up a vacuum pump to the valve (Ok to be installed on veh) and insure its holding vacuum.
You’re throwing a lot of parts at this problem. You have a vacuum leak somewhere, you have to test every piece before replacing. Putting grease on the seal of the gas cap can test that part. Smoke testing is the best way to find a stubborn vacuum leak.
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