Expert: Robert Summers - 4/17/2008

Question
For a 1999 Chevy Tahoe (5.7L Auto), my computer shows Error Code P0442 (EVAP System Small Leak (0.040") Detected). I have already tightened the fuel cap but the Sevice Engine Soon light has not turned off. A couple of questions:

1) How long should it take for the error to clear by itself if the problem was the loose fuel cap?

2) Can I clear the code without disconnecting the battery?

3) Assuming the code does not clear (or reappears after I reset it), would you suggest replacing the fuel cap or should I first look to other sources of leakage such as moisture in the charcoal canister, leaks in the fuel tank, filler neck or fuel sending unit O-ring, a damaged pressure sensor, a clogged vapor line or purge valve, a leaking or sticking purge solenoid or vent solenoid, or a bad PCM?  

Answer
Hi Rob...you will need to clear codes via scan tool... disconnecting battery will not clear code...if it is loose cap problem it should go away in about a tank of fuel...if it comes back all your thoughts are  good... i would start with the cap...hope this helps