2 codes, please help!!

[roblo101]

Hello all,
I enjoy these forums, alot of really good an interesting info.
I have a 96 chevy 1/2 ton, 5.7 w/ auto trans. about 175000 miles.
Last year replaced intake gasket, and went ahead an had both heads done. Over the last 2-3 years I have replaced all the O2 sensors also.

Now it is nice enough to throw me a couple of codes.
Not sure about these,
First one is: PO430 catalyst system efficiency below threshold, bank 2....

Second one is: PO131 O2 sensor circiut low voltage, bank 1 sensor1...

Now that o2 sensor on passenger side was the last o2 replaced, I know
they don't last forever. At the price, they should, ha!

These two codes have me puzzled, I try to do all my bolt turning myself.
Would appreciate any an all feedbacks,

And by the way, I'm new to this forum, a big Howdy to all, from Texas!!

Thanks for ya'lls time with this one
Rob

[tblake]

Hey Rob!

What brand sensor did you go with? I try to stay away from Bosch everying. GM motors don't get along with bosch.

Since you have a 350, you have 4 O2 sensors, right?

for the P0131, I would check to make sure the O2 sensor wires are not rubbing the body or contacting the exhaust.

Then I would swap the front O2's side to side, then do the rear ones side to side, and have the codes cleared. Drive it like this untill the SES light comes back on (if it does). When it comes back on, if you still get P0131 and P0430, I would suspect a wiring issue with the vehicle harness causing the P0131, and a bad cat converter causing the p0430.

However if now you get P0151 (O2 sensor circuit low voltage bank 2 senosor 1) and P0420 (catalyst effiency below threshhold bank 1), you will know your issue is the O2 sensors.

I hope that makes sence.

BTW, welcome to AF!!!!

[roblo101]

Hey
Thanks for responding so quickly!
And yes I have four sensors, and yes, replaced all with Bosch???
What other name brand is there, are better yet, in your opinion
a better one?
And I will try your advice this weekend, it did make sense,
Thanks
Rob

[tblake]

I hardly ever replace the rear sensors in anything of mine unless there is an issue with it. The rear O2's are only there to monitor the Cat Effiency and it has nothing to do with drivability. If you have the old rear ones still, try swapping those back in.

The front O2 sensors in my pickup are both Denso brand. No issues, but the darn things were about 75 bucks each. With O2 sensors I usually stick with stock delco's or denso I have had good luck with. I got my Denso's from AutoValue and they come with a 2-yr warrenty.

Which your bosch O2's could be under warrenty also.

Let us know how things turn out.