Code P0442? Help Would Be Appreciated

koz85037 · March 29, 2011

Hi guys, I keep getting a check engine light so I took my 2004 silverado to my local autozone, and came up with code P0442. I have done some research and found out that it is a small evap leak. I seen one hose that went to engine that had a split running down it so I took that off and replaced it. I changed out the gas cap, inspected all the other hoses and I dont see anything that looks bad, but I still have the CE light on.( the CE light comes on and goes off it seems to last for about a week at a time) Then I ran my engine and sprayed carbuerator cleaner everywhere to try to detect a leak.. and nothing. I have been reading on here and seen guys talking about a Vent solenoid valve maybe the culprit? Is there a way to test to see if mine is faulty. I am a novice but have decent understanding and common sense . Thanks for any help. Rob

donjames911 · March 29, 2011

Hi guys, I keep getting a check engine light so I took my 2004 silverado to my local autozone, and came up with code P0442. I have done some research and found out that it is a small evap leak. I seen one hose that went to engine that had a split running down it so I took that off and replaced it. I changed out the gas cap, inspected all the other hoses and I dont see anything that looks bad, but I still have the CE light on.( the CE light comes on and goes off it seems to last for about a week at a time) Then I ran my engine and sprayed carbuerator cleaner everywhere to try to detect a leak.. and nothing. I have been reading on here and seen guys talking about a Vent solenoid valve maybe the culprit? Is there a way to test to see if mine is faulty. I am a novice but have decent understanding and common sense . Thanks for any help. Rob

If Autozone didn't clear the error from the OBD, it will continue to give you the 'check engine' light even though the problem has been corrected.

spock · March 30, 2011

I have had the PO442 several times and was told that it is almost always a bad gas cap or the cap not sealing well on the filler neck. I have a little ding on the filler neck and I don't feel like changing it out. It can take several drive cycles for the code to clear. mine has a habit of throwing the code just when I'm due to get the yearly inspection.

frdfandc · March 30, 2011

There is more to the Evap system than just a fuel cap and hoses. There are also solenoids and valves, and the fuel tank as well that are included in this. Usually with a small Evap leak it is the fuel cap seal, but can be deteriorating hoses as well. So crawl under the truck and check all the Evap lines from the tank.

Sometimes with this code (but not normally) the entire Evap system needs to be smoked (a smoke machine is used to detect leaks) and the solenoids/valves need to be check to determine what the problem is.

I had the same code on my 2003. Mine ended up being an Evap Shutoff solenoid that wasn't operating properly when the Evap self test was performed on first startup. It was an updated part.

koz85037 · March 31, 2011

There is more to the Evap system than just a fuel cap and hoses. There are also solenoids and valves, and the fuel tank as well that are included in this. Usually with a small Evap leak it is the fuel cap seal, but can be deteriorating hoses as well. So crawl under the truck and check all the Evap lines from the tank.

Sometimes with this code (but not normally) the entire Evap system needs to be smoked (a smoke machine is used to detect leaks) and the solenoids/valves need to be check to determine what the problem is.

I had the same code on my 2003. Mine ended up being an Evap Shutoff solenoid that wasn't operating properly when the Evap self test was performed on first startup. It was an updated part.

Thanks for the responses guys. Fordfandc how did you diagnose your Evap shutoff solenoid? and is there a do it yourself friendly way to smoke test my truck without bringing it to a shop. Thanks in advance.