Cat question?

[roblo101]

Hello all
Really good forum here, alot of nice reading, thanks.

I have a 96 Chevy ext cab, 5.7 1/2 ton truck. Bought this truck new, been a good truck. In the last 2-3 yrs, changed all 4 O2 sensors, had heads reworked, (intake gasket leaking) had heads done while they were off. An finally had to install fuel pump. 175,000 miles

Have had 1) code PO430 eff below threshold, Bank 2 (cat)

Now have three more, and really poor mileage!

2) PO151 o2 circuit to low, bank 2 sensor 1

3) PO420 eff below threshold, bank 1 (cat)

4) PO131 o2 circuit to low, bank 1 sensor 1

Question is: Should I replace both cats?

And if so, can I use the aftermarket free flow, or what do you advice?
I have a buddy thats a welder, thats no problem.

And does these 2 codes mean the o2 sensors need replaced, or by
replacing the cats, it will help them clear themselvs????????
As high as they are, they should, ha!

Thanks for any an all advice with this, and by the way, it is
original exhuast.
Thanks again
Rob

[mechanic1980]

Check the trans shift linkage if the gear selector switch on the trans isnt lining up right the trans wont shift differently when cold which it does in order to heat the cat up faster sounds crazy but ive seen it before this will cause the p0430 code which in turn may cause either lean or rich codes as well trying to correct the cat issue. If the linkage is good get a temp on the cat front and rear after truck is hot with engine running if temp is the same cat is bad. As far as replacing the O2 sensors you need to check the connectors first loose connection = low voltage

[j cAT]

Originally Posted by roblo101

Hello all
Really good forum here, alot of nice reading, thanks.

I have a 96 Chevy ext cab, 5.7 1/2 ton truck. Bought this truck new, been a good truck. In the last 2-3 yrs, changed all 4 O2 sensors, had heads reworked, (intake gasket leaking) had heads done while they were off. An finally had to install fuel pump. 175,000 miles

Have had 1) code PO430 eff below threshold, Bank 2 (cat)

Now have three more, and really poor mileage!

2) PO151 o2 circuit to low, bank 2 sensor 1

3) PO420 eff below threshold, bank 1 (cat)

4) PO131 o2 circuit to low, bank 1 sensor 1

Question is: Should I replace both cats?

And if so, can I use the aftermarket free flow, or what do you advice?
I have a buddy thats a welder, thats no problem.

And does these 2 codes mean the o2 sensors need replaced, or by
replacing the cats, it will help them clear themselvs????????
As high as they are, they should, ha!

Thanks for any an all advice with this, and by the way, it is
original exhuast.
Thanks again
Rob

at this mileage it is common for the cat converter to go .
since you had gasket failures this will also cause these converters to get damaged...

whenever replacing the cat converter the upstream sensors should be replaced as well as any engine componets that could cause an incorrect fuel mixture/ burn condition..your vehicle is at the point where the distributor may be defective as the bearings go at this mileage ..

[tblake]

What brand O2 sensors did you go with. If they are bosch, I'd be half tempted to swap the stockers back in there, clear the codes, and see if anything comes back.

[roblo101]

Hey Guys
Thanks for the fast response.
I did buy the bosch o2 sensors, and since have heard several bad things about them. What other brand should I try, if/when they need replaced.
I
When putting motor back together, did change the gear at end of dist shaft.
Where can I order/purchase aftermarket or replacement cats?
And please tell me a few good brand names, they sure are alot out there!

I did also check the linkage at trans, looked like still right, thats for that tip.

Thanks again
Rob

[777stickman]

To add to the previous replies: Delphi/AC Delco 02's are the best.

Also what brand fuel pump did you put in? Again Delphi/AC Delco is the best. If it's an Airtex you may have issues with fuel pressure, so that also needs to be checked regardless of what brand the pump is.

For now I would believe the O2's until you can eliminate all other issues that would trigger these codes. Both the P0131 & P0151 indicate a lean condition on both banks from the upstream sensors.

Typical reasons for these codes are:

1. Low fuel pressure.
2. Vacuum leaks.
3. Exhaust leaks upstream of the O2 sensors.
4. Bad MAF sensor.

[roblo101]

Hey stickman
I did use a Delco brand fuel pump.
Have a couple of questions, please?
the codes PO430 an PO420, is these the cat's itself?

And the other 2, is the bank1 an bank 2 the left/right side, right?

And when it says sensor 1, is this closest to the engine?

I will check the things you suggested, thanks!

Rob

[777stickman]

Originally Posted by roblo101

Hey stickman
I did use a Delco brand fuel pump.
Have a couple of questions, please?
the codes PO430 an PO420, is these the cat's itself?

And the other 2, is the bank1 an bank 2 the left/right side, right?

And when it says sensor 1, is this closest to the engine?

I will check the things you suggested, thanks!

Rob

Sensor 1 is before the cat and 2 is after the cat.
Bank 1 is drivers side and 2 is pass side.

420 & 430 could be the cats, but I would concentrate on finding the lean issue and maybe the 420 & 430 will go away when that is found and fixed.

Good luck to you.

[jonnik]

I'm surprised the cats have lasted as long as they have. Rockauto.com has bolt-on, direct replacement cats for under $400. Being in Texas (Go Blue Bell!) there will be no legal issues (not for California, blahh, blah). I ordered cats for a '98 Tahoe and they were pretty easy to swap, just remember to get the gaskets.