GMC Acadia Forum banner
1 - 7 of 7 Posts

· Registered
Joined
·
25 Posts
Discussion Starter · #1 ·
Hello all, I know I usually ask some bogus questions here but I really do need some assistance. My Acadia has been throwing P0430 and P0420 codes for a while now and I don’t know what the problem is. I replaced the Catalytic Converters between the engine and the firewall along with the one between the engine and the radiator in October of 2021 and replaced the upstream O2 sensors when I changed them out. I had change out the downstream sensors maybe a couple months before then. I also replaced the Y-pipe with all of this as well. I just recently replaced the downstream sensors because I thought the problem was coming from those but the codes are still coming back. Should I replace the upstream sensors too and hope that my problem goes away or do I replace the converters again period? I meant to add that the codes started throwing probably around spring of 2022, maybe over the summer, I don’t remember exactly when but they started a couple months after replacing the majority of the exhaust. I should also probably add that I have had the exhaust unbolted at the end of the y-pipe, going towards the muffler, I’ve done it a couple times because I’m an idiot who thinks it sounds good without thinking about the repercussions. I never had it unbolted for more than a few days though before putting it back together and snugging everything up and leaving it for a while. Could my stupid actions be the cause of my problems? Could it be something else? I really need help because my tags expire next month and I’m pretty sure I’m due for emissions this year since my car is an ‘09.
 

· Registered
Joined
·
3,487 Posts
Never mess with disconnecting factory exhaust parts. And. . . . yes, that or whatever was done could possibly set codes.
Maybe time to take it into a repair shop for further diagnosis and repair.
 

· Registered
Joined
·
4,223 Posts
Never mess with disconnecting factory exhaust parts. And. . . . yes, that or whatever was done could possibly set codes.
Maybe time to take it into a repair shop for further diagnosis and repair.
I agree. Sometimes you have to wonder what folks are thinking.

You muck with the exhaust on modern vehicles, you can expect to throw trouble codes.
 

· Registered
Joined
·
2 Posts
I had a similar issue with my 2011. The bottom line was 2 new cats and a new Y pipe(flex had a hole too), Had help from a friend at a local automotive shop in the process and a lot or research on the internet,

The first thing you need to do is stop throwing parts at a problem without diagnosing it properly.

You need a Good Diagnostic code reader that permits you to see what is actually going on with the O2 sensors in real time. You need to understand the inter relationship between the sensors and their readings. Then ANY type of Exhaust leak, even a pin hole in the flex joints can cause issues.
You said you replaced the Cats. Were they GM parts or aftermarket. If you live in a state where they do emissions testing than you need to go with the GM Cats,
Histories show that the after market ones don't perform well over time and the GMC programing is set very tight so the slightest off signal will trip a code. Saving a few dollars initially will cost you double in the long run.
Also some aftermarket cats and pipes have issues with where the O2 sensors are mounted. The height at which the sensor is critical and some techs report that they had to add an extension spacer to get good readings from the O2 sensors.
Back pressure on the system is critical for proper operation. Changing the OEM design can cause issues. Removing a section is not advisable or a good idea. Driving the vehicle for an extended period will damage the Cats too and they will not be able to regenerate themselves.
Once you know what is going on then you can fix the issues. Also don't rule out an ECM issue or wiring issues. All of which can be diagnosed with a professional diagnostic tool.
My$.02. Hope this helps and Please keep us posted.
Steve D.
 

· Registered
Joined
·
25 Posts
Discussion Starter · #6 ·
Aftermarket CATs or OEM? I know of a lot of aftermarkets that will burn out in a year or two.
They are straight from GM but they are aftermarket’s I got off Amazon. I’m sure that doesn’t help my case though.

I was talking to one of my roommates and he proposed the idea that since the Acadias have 3 Cats that maybe the 3rd one after the y-pipe is clogged up and sending emissions back up the exhaust to the sensors therefore throwing off the computer. Could this be an actual problem to look into? I have a replacement for the 3rd cat but I don’t have a welder to put it on the exhaust so anything after the y-pipe wasn’t touched when I did exhaust work.
 

· Registered
Joined
·
25 Posts
Discussion Starter · #7 ·
Hello all, I know I usually ask some bogus questions here but I really do need some assistance. My Acadia has been throwing P0430 and P0420 codes for a while now and I don’t know what the problem is. I replaced the Catalytic Converters between the engine and the firewall along with the one between the engine and the radiator in October of 2021 and replaced the upstream O2 sensors when I changed them out. I had change out the downstream sensors maybe a couple months before then. I also replaced the Y-pipe with all of this as well. I just recently replaced the downstream sensors because I thought the problem was coming from those but the codes are still coming back. Should I replace the upstream sensors too and hope that my problem goes away or do I replace the converters again period? I meant to add that the codes started throwing probably around spring of 2022, maybe over the summer, I don’t remember exactly when but they started a couple months after replacing the majority of the exhaust. I should also probably add that I have had the exhaust unbolted at the end of the y-pipe, going towards the muffler, I’ve done it a couple times because I’m an idiot who thinks it sounds good without thinking about the repercussions. I never had it unbolted for more than a few days though before putting it back together and snugging everything up and leaving it for a while. Could my stupid actions be the cause of my problems? Could it be something else? I really need help because my tags expire next month and I’m pretty sure I’m due for emissions this year since my car is an ‘09.
Update, replacing the 3rd converter did not help at all. I’m still getting the P0430 and P0420 codes
 
1 - 7 of 7 Posts
Top