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Just had my "Check Engine Light" come on in my 2000 C5. When I checked for codes, I found the following: 10PCM P0442 Evaporative Emission (EVAP) system small leak detected. I was also low on fuel and had the "Low Fuel" message on the DIC, so I stopped and filled the tank. The fuel cap seems to be working fine. Any thoughts on what the issue might be?
that code is for a small leak. Often just a new fuel tank cap and 10 ignition cycles or a drive cycle will clear the CEL. THe GM drive cycle can be found in a google search. However there are actually several possibilities, the gas cap the most common
You may have a bad fuel cap, leaking purge or vent valve or their hoses....small leaks are sometimes difficult to diagnose even with right equipment...good luck !!
If someone with a Tech2 or another bi-directional scan tool can help you out it is possible to verify if the EVAP Vent valve and the EVAP Purge Valve operates .
With a tool like mentioned the fuel tank pressure can be observed while these valves are operated manually with the scantool .
The Purge Valve is in the engineroom and the EVAP vent valve is under the car in the right back shown in the photo .
If the vent valve are closed on command by the scantool the tankfuel pressure wil go more negative ,
With the car idling and Vent valve open I observed appox. 1.5 volt from the fueltank pressure sensor (-0.84mmHg ) increasing to 2.6 volt (-9.27volt) when I closed the EVAP Vent valve for some seconds.
A lot of good information, Thanks to all. When I parked my car in the garage yesterday, the smell of gas fumes was overwhelming. I had to open the garage door a few inches to allow the fumes to escape. Went out and purchased a new gas cap last night, and noticed no more fumes in the garage after swapping caps. I live in Denver CO and we had snow last night, so I need to wait a couple days to perform the Basic Drive Cycle. I'm hopeful the problem was the gas cap and the drive cycle will resolve. Snow today - it will be close to 60 degrees on Thursday and Friday (Denver weather is crazy).
DIC Code P0442
