i have a 2004 buick lesabre custom v-6 3.8 with 39,000mi.bought in aug. 07.went to autozone when service engine light came on ( thanks to you guys) that was 2mons. ago.got readout with symptoms & definitions went to my mechanic,he said to hold off. 2 days later service engine light goes off. has not returned. yet?? recently service engine light comes on again, go to autozone code po442.get readout & definitions & symptoms. was keeping an eye out while driving for read out problems nothing?? 4to6days later.while i was in autozone young guy overheard my situation said to put lubricate on rubber seal on gas cap. what did i have to lose?? put it on, next day light goes out driving down expressway. the car is running very good. my question to you guys???by not quickly taking care of the codes will they come back to bite me down the road . i"m sure they will be back. how long do i hold off??? this is all worrysome to me. my other cars & truck are oldies. they don"thave these code plugins stuff to worry about.thanks for any replys to joesph meehan i will put in no caps i was warned before. only kidding joe!!! to everyone have a great holiday
Thanks for no All CAPS.
I am not sure what P0442 means in your car, but if it is a vent issue, it could be nothing more than a poorly sealing gas cap. The response of the young guy (at my age almost all of them are young) at Autozone tends to indicate that it is a related problem and his suggestion may fix it. You don’t want to keep ignoring any code because even if you know it is not all that important to you, if the light is on all the time you will never know when another really important code is generated.
Next lesson. Using capital letters at the beginning of a sentence and leaving a space after the period at the end does help, but it is not nearly the problem ALL CAPS are. 
The PO134 is upstream oxygen sensor, no activity detected.
The PO442 code means: EVAP, small leak detected.