Newbee with code questions

[Tooltime]

First post, I just got a 1998 GMC Sierra Z71 with the 5.7/auto with 180,000 miles. I traded a guy even up for a car I had. I needed a pickup and he wanted my car, so it worked out for the both of us. I've always loved the body style,I had a 99 chevy and regretted selling it,but always liked the look's of GMC more so I got what I really wanted. So just a couple of days ago the CEL came on and I took it over to Auto Zone to have them pull the codes for me. Here's what they came up with.

PO141 Oxygen sensor defective
Poor connection@ O2 sensor
Check circuit fuse

PO430 Catylitic converter defective
Engine missfire
Large vacuum leak
Engine oil leakage into exhaust valve guide

I think the second code is the result of the first code because the truck still runs fine, no missfire, and if I had a large vacuum leak I would know it.
I do have a vacuum guage and will check for a leak when I have time.

I'm posting to see if this is a common problem and ask for advice.I'll start by checking the circuit fuse,but where can I find the circuit fuse for the O2 sensor?
Thanks in advance. TT

[mudseeker]

p0141 is a heater circuit problem, most likely a bad o2 sensor.

second code is for low cat efficiency, doesn't mean it's bad, just getting old and is past the point of what the epa considers good.

[ukrkoz]

well, silly as it sounds, let me try saving you a buck or 2.
buy new gas cap.
buy can of seafoam.
find a gas station next to freeway, chevron or shell or texaco, or exxon.
run your tank to refill condition.
get yourself a narrow funnel.
go to that gas station, pour seafoam in using funnel, refill tank; while it's filling, remove negative from battery. should be enough time to reset codes. if possible, use code reader to reset codes.
refill, replace cap with new one, and get truck on freeway, for about 30 min doing 60-70, just to blow that seafoam through the system.
see what happens. worked well on several cars.

[ThunderDawg09]

Not sure if I can really help. But welcome to the forum!

[Tooltime]

Originally Posted by ukrkoz

well, silly as it sounds, let me try saving you a buck or 2.
buy new gas cap.
buy can of seafoam.
find a gas station next to freeway, chevron or shell or texaco, or exxon.
run your tank to refill condition.
get yourself a narrow funnel.
go to that gas station, pour seafoam in using funnel, refill tank; while it's filling, remove negative from battery. should be enough time to reset codes. if possible, use code reader to reset codes.
refill, replace cap with new one, and get truck on freeway, for about 30 min doing 60-70, just to blow that seafoam through the system.
see what happens. worked well on several cars.

Thanks, that's what I was looking for, a little trick to save some bucks and what to watch out for. Thanks again for all the responses. TT