OBDII code issues

[66mike]

new to this group - looking for some help before I lose my mind.
96 K1500 w/5.7Vortec, 100K miles - runs great but intermittent rough idle/idle up/bangs in 1-2 shift... will throw the same codes every time. P0122 and P0134 (TPS and O2 bank1 upstream)

I've swapped out 3 TPS sensors and when I check voltage I get 5V, so I'm suspecting the TPS is not the cause, it's being affected by something else that is stealing voltage from it? I already installed a new fuel pump, pressure approx. 60psi, visual wire inspection of TPS harness & O2 connector appear OK but haven't swapped out O2 sensor yet. Truck will run 100% for a day or so, and then randomly this issue will re-appear, doesn't seem to matter if it's warm or cold. Turning off ignition & re-start will immediately correct it, and after 3 starts CEL will go out on it's own. It seems to be down on power & my fuel mileage is horrible, even for these trucks. (no better than 10mpg)
If I swap out suspect O2 and problem persists, is PCM ground possibly the next place to look? I've replaced all the engine/chassis/frame grounds with #6 welding wire so grounds appear to be all good.

Help... this is driving me nuts.

 

[Tom P]

Having a Bad O2 sensor is enough to drive you nuts, and I'm fighting some similar issues, but if your sensors haven't been replaced lately, you might as well do the job. Either use Denso or ACDelco Original Equipment which can be found on Amazon for reasonable money. You obviously have a scanner, so check and see what else is going on if you have live data capabilities. Is your fuel system making it into close loop? What do your fuel trims look like?

 

[east302]

Here are the diagnostics for P0122 for a 98, maybe it will help.

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White (clear) C3 connector:

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[east302]

And P0134...

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[66mike]

And P0134...

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thanks for the input guys.... clearly I have more diagnostic work to do..... I'm going to start with the simple stuff first, as I discovered I do have a small exhaust leak at the manifold donut right upstream of the O2 sensor on bank 1.
If that doesn't address it, I'll dive in deeper......

 

[66mike]

Having a Bad O2 sensor is enough to drive you nuts, and I'm fighting some similar issues, but if your sensors haven't been replaced lately, you might as well do the job. Either use Denso or ACDelco Original Equipment which can be found on Amazon for reasonable money. You obviously have a scanner, so check and see what else is going on if you have live data capabilities. Is your fuel system making it into close loop? What do your fuel trims look like?

I don't have a live scanner but can borrow one - unknown about the fuel loop/trims... replaced the OEM pump/sending unit a while back but I recall having the issue occasionally before that.... however I have discovered that an exhaust leak upstream can cause the O2 issues, and I do have one at the donut as it turns out.

 

[Tom P]

I don't have a live scanner but can borrow one - unknown about the fuel loop/trims... replaced the OEM pump/sending unit a while back but I recall having the issue occasionally before that.... however I have discovered that an exhaust leak upstream can cause the O2 issues, and I do have one at the donut as it turns out.

I think most guys have a leak there. They were notorious for leaking and more than a pain in the @$$ to fix unfortunately too. Start with a scanner with live data and go from there. If you have a good smart phone or tablet, consider a bluetooth/wifi obdii transmitter that you find on Amazon and then buying a $9.99 app. Most decent homeowner stand alone scanners are 45-75 bucks, so the smart phone style can give you more bang for your buck.

 

[66mike]

Having a Bad O2 sensor is enough to drive you nuts, and I'm fighting some similar issues, but if your sensors haven't been replaced lately, you might as well do the job. Either use Denso or ACDelco Original Equipment which can be found on Amazon for reasonable money. You obviously have a scanner, so check and see what else is going on if you have live data capabilities. Is your fuel system making it into close loop? What do your fuel trims look like?

I think most guys have a leak there. They were notorious for leaking and more than a pain in the @$$ to fix unfortunately too. Start with a scanner with live data and go from there. If you have a good smart phone or tablet, consider a bluetooth/wifi obdii transmitter that you find on Amazon and then buying a $9.99 app. Most decent homeowner stand alone scanners are 45-75 bucks, so the smart phone style can give you more bang for your buck.

thanks Tom...

 

[66mike]

thanks for the input guys.... clearly I have more diagnostic work to do..... I'm going to start with the simple stuff first, as I discovered I do have a small exhaust leak at the manifold donut right upstream of the O2 sensor on bank 1.
If that doesn't address it, I'll dive in deeper......

 

[Tom P]

thanks for the input guys.... clearly I have more diagnostic work to do..... I'm going to start with the simple stuff first, as I discovered I do have a small exhaust leak at the manifold donut right upstream of the O2 sensor on bank 1.
If that doesn't address it, I'll dive in deeper......

Hopefully you have good luck fixing your exhaust leak. My truck was originally from BC and if they use salt in Ontario like they do in BC then you are going to have fun getting those nuts off. I have thought about beginning the adventure myself a time or two and every time go to put a wrench on it I realize how little time I have to dedicate to finishing the job, if stuff goes south.