No mention about how much oil is it consuming. When was the oil changed last? Confirmed that proper amount was put in at the time?

 

Oil light came on with oil off of the dipstick, not sure what that means for how low. Oil was last changed about 3500 miles ago. I've been checking the oil and it seems like the consumption was all of sudden. There have been a few long trips recently so perhaps AFM.

 

What troubleshooting have you already accomplished?

 

For this current issue, all I've done is read the code. I do have a scan tool. Since it's a cat issue, according to the code, I'm not sure what to do. I'd like to make sure it really is a cat issue, and if it is, was there something, like high oil consumption, that caused it.

 

If you’re consuming oil and you have a cat issue, me thinks that the oil is blowing around the rings and dumping right into the cats. Just like the Chevy Equinox and GMC Terrain are known to do

 

Any way to test that theory?

 

Did you change the oil yourself? If not did you check it after they were done? L83’s hold 8 quarts and I have started changing it myself because the last two times I’ve gotten it changed it was a little over 2 quarts low, both times they tried to argue with me about it being low. If you don’t have a place and/or the tools to do it yourself check it before you leave.

 

I do the changes myself and oil level has been good for a couple thousand miles until now.

 

Have you pulled the air filter box apart since it started swallowing oil? I’ve heard of these pushing oil back through the intake when the PCV system is malfunctioning. My sons 2012 Impala LTZ with the 3.6L is notorious for this and that’s why I installed an Evil Energy oil catch can on it because his car was doing that when I bought it for him.

Or you have the stuck piston ring issue that the AFM is known to cause, Google it and you’ll see the complaints.

On my 2016 Sierra with the 5.3, I installed a Range AFM bypass into the OBD-II port the day I bought the truck because of the known issues. Deep down inside, I know the engine still has the mechanical parts of the AFM which is why I will be going to the Texas Speed AFM delete kit. That includes a slightly hopped up camshaft, new lifters, plugs for the AFM ports in the top of the block, and a custom tune for the new parts that also fully deletes the AFM from the truck permanently.

It’s a shame that GM is having these issue as I always assumed the LS based V8’s were bullet proof. I was a Ford guy, loyalty to my dad as he worked there for 43 years lol, up until 2015 when I bought my first GM truck. I thought Ford was the only ones with big problems in the V8 platform

 

Have you pulled the air filter box apart since it started swallowing oil? I’ve heard of these pushing oil back through the intake when the PCV system is malfunctioning. My sons 2012 Impala LTZ with the 3.6L is notorious for this and that’s why I installed an Evil Energy oil catch can on it because his car was doing that when I bought it for him.

Or you have the stuck piston ring issue that the AFM is known to cause, Google it and you’ll see the complaints.

On my 2016 Sierra with the 5.3, I installed a Range AFM bypass into the OBD-II port the day I bought the truck because of the known issues. Deep down inside, I know the engine still has the mechanical parts of the AFM which is why I will be going to the Texas Speed AFM delete kit. That includes a slightly hopped up camshaft, new lifters, plugs for the AFM ports in the top of the block, and a custom tune for the new parts that also fully deletes the AFM from the truck permanently.

It’s a shame that GM is having these issue as I always assumed the LS based V8’s were bullet proof. I was a Ford guy, loyalty to my dad as he worked there for 43 years lol, up until 2015 when I bought my first GM truck. I thought Ford was the only ones with big problems in the V8 platform

First off, I too was a Ford guy with similar ties. The Chevy has been much easier to work on, just wish it wasn't so often!

No, haven't pulled the air box. Will add that to the list.

I am thinking about the OBD AFM "delete," but am wondering if I should just skip to true delete. If I knew that's what was causing problems, I'd probably just dive in. I also wonder if it's worth it with so many miles.

Is there a way to test for stuck ring? I'd like confirmation of the problem.

 

what o2 sensors did you put on ? (by brand) did you replace all of them ?

the p0420 is easy to get,...a nothing that nags. you may have to monitor and see if there is something happening for a short period, ...and almost causing a unique code,...but the only one being thrown is the p0420

 

NTK sensor and on the same bank of the code.

I have wondered if that's the problem.

 

What ever happens with Equinox/Terrain is not directly applicable to the truck OP has. Yes, it's plausible that a ring issue could cause cat to get clogged, but these engines are not prone to ring issues. So, I would take that with a grain of salt.

Clogged cat is easy to diagnose with an infrared thermometer. If a cat is clogged, it will run much hotter than others.

With regards to the oil consumption, I'd just fill it up to proper level and keep an eye on it for now if you don't have any other issues.

 

As a firefighter, I have access to IR cameras. I'll take your advice and use that to investigate.

 

Did it start drinking oil after the catch can install?

Pull the plugs one by one to see if it’s isolated to one cylinder or all. This may be hard to tell if it just started though.

 

No, oil consumption started at least 1000 miles later

 

Oi consumption will cause a P0420/ P0430
Sounds like it is on the one bank side ( Bank 1)
You said you replaced PCV , how did you do that? what did you replace ?

 

I just replaced the PCV valve.

 

My working theory is that my catch can filled up (oops), then dumped oil into the system and messed with cat (hopefully not too bad - can it be cleaned?). I'll get the J&L catch can extension and replace 02 sensors with GM (not that much more expensive when ordered online).

Am I on the right track? Should I look at anything else?

 

02 sensor update and PCV valve being swapped today along with an oil change. Will report back for those paying attention.

 

Yes, GM/ACDelco has used both suppliers fgor o2 sensors.

 

Davester3500 is correct! Many suppliers that GM uses in the pipeline but most say AC Delco or Denso on them

 

NTK and denso are good Brands.
I have installed a LOT of NTKs in everything from toyota to chevy
Never a problem

 

Update: new o2 sensors installed. So far no "cat code", but I did get a P0107 ( Manifold Absolute Pressure (MAP) / Barometric Pressure Sensor Circuit Low Input). Maybe related? Maybe not? Will do some research and then probably start a new thread

 

So....MAP sensor code was my mistake if forgetting to plug it in
Back to oil consumption. Just drove 350 miles and it's probably down 2 qts. There's probably 1 tablespoon of oil in catch can.
I'm not scared of putting new engine in or even rebuilding it. But before I dive in, I'd lto know for sure what's wrong. Thoughts?