CEL for P0420, P0430, P0171, P0131, P0134

[donjetman]

I had P0171 once caused by the air intake tube being loose.
Here's the thread I did with pic: https://www.tahoeyukonforum.com/thr...ight-no-misses-or-issues.145019/#post-1829514

 

[07burban88]

change the down stream sensors before replacing the cats. even if it still has cat codes after the down streams, ya needed the sensors anyway as they need to be replaced when the cats are replaced for proper readings

 

[j91z28d1]

For starters, the lowest two codes are for the driver's side upstream oxygen sensor.

There's three possibilities here as to why it's throwing codes, the sensor is no good, the wiring needs repair, the ECM is needs replacing. Solve this and the P0171 will probably go away.

You at least need a good OBDII adapter that can clear codes and show you all the engine data.

I use BT and WIFI Foseal ODBII adapters and pair that with my Android phone and the Torque Pro app. My kids have IPhones and use the CarScanner app from the Apple Store, it's free for them. I paid $5 for mine about 8 years ago.

I can only see engine stuff with my phone and app, my kids can see ALL codes from anywhere in the car and clear them with their IPhone and app.

car scanner app is available for android too. but I like tq better and I am able to add extra pid's in it to read other modules info. super easy for a daily use kinda thing. the dongle you have makes a differences too, some cheap ones are good and can do commands while others can bearly read the basic ecm stuff. even those the case looks exactly the same.
I did recently upgrade my 2014 car from a 30$ to a 50$ one, since the app I use for it got updated to add some specific bidirectional commands and the cheaper one couldn't do it. the app developer used that model for his development. so figured it was worth it. that app is 20$ alone thou.


I'm pretty sold on the 130$ gear wrench one. it shows a lot of stuff for cheap, is very easy to use, has bidirectional commands and no update fees. 3 people I know have got it, and are happy with it for keeping it in the car type of thing. leave the expensive stuff locked up at work. I probably have access to 6 different scanners between home and work. for quick check on data on my daily's especially how the hybrid batteries are doing I use tq, but at work, I always grab the gearwrench long before pulling out the laptop based high end stuff.

the tech 2 I haven't touched beside programming new fobs in a good year. (knock on wood)

 

[thefrey]

Update:

New upstream O2 sensors stopped the lean code 0171 and any sensor codes 131, 134, 015B

I now have a lingering 420/430 code. I cleared it and did 700 miles highway (on a 1200 mile trip) on a roadtrip with no code, stopping a couple of times, and it popped up when I was coming to a stop at a stoplight.

I’m not sure if it’s a cat issue or what. I think it’s odd that it took 700 miles for it to come up and that it’s both cats and not just one, unless they are both failing at the same time?

I don’t have emissions in my state so I don’t know if replacing them is what I want to do. But if I can revive them somehow I would like to just for peace of mind.

 

[OR VietVet]

Update:

New upstream O2 sensors stopped the lean code 0171 and any sensor codes 131, 134, 015B

I now have a lingering 420/430 code. I cleared it and did 700 miles highway (on a 1200 mile trip) on a roadtrip with no code, stopping a couple of times, and it popped up when I was coming to a stop at a stoplight.

I’m not sure if it’s a cat issue or what. I think it’s odd that it took 700 miles for it to come up and that it’s both cats and not just one, unless they are both failing at the same time?

I don’t have emissions in my state so I don’t know if replacing them is what I want to do. But if I can revive them somehow I would like to just for peace of mind.

IIRC, there is some snake oil that is out there for "revitalizing the cats". I hate stuff like that, so am not gonna go looking but you can search of course.

I lied, here is a few:

5 Best Catalytic Converter Cleaners of 2026 - Top-Rated Reviews & Deals

 

[thefrey]

IIRC, there is some snake oil that is out there for "revitalizing the cats". I hate stuff like that, so am not gonna go looking but you can search of course.

Yeah, I am not sure if I want to go that route or not yet. I was curious if anybody had had any luck with stuff like that.

It seems to fall in the category of “probably doesn’t hurt, might help”

I might try it just to try it and see if it works at all.

 

[OR VietVet]

Yeah, I am not sure if I want to go that route or not yet. I was curious if anybody had had any luck with stuff like that.

It seems to fall in the category of “probably doesn’t hurt, might help”

I might try it just to try it and see if it works at all.

I just edited my post and added a link.

 

[thefrey]

IIRC, there is some snake oil that is out there for "revitalizing the cats". I hate stuff like that, so am not gonna go looking but you can search of course.

I lied, here is a few:

5 Best Catalytic Converter Cleaners of 2026 - Top-Rated Reviews & Deals

Well, I tried to run one of these and drove the piss out of it on the highway to get my exhaust temps up... no luck. Seems my 420/430 codes are here to stay.

Now to figure out if it's cat related or something else. Downstream o2 sensors are showing a nice sine wave. If it's cats, it's interesting that both went at the same time, though...