Howdy,
I have a 2006 Pontiac Grand Prix with an L26 (Buick 3800) that is well over 200k miles. I've replaced the catalytic converter with a new aftermarket Walker converter and I've replaced both upstream and downstream O2 sensors from ACDelco. It is still throwing P0420 and there are no exhaust leaks. Is there anyway to fix this besides using the O2 sensor spacer hack?
I'm planning on registering the car in West Texas where there is no emissions testing, so I'm not too worried about it, but I figured I would try to find a fix.
did you make sure the sensors are reporting correctly using a scan tool?
Just checked the data on my scanner and it's showing that both O2 sensors are working. Idk what voltage should be on the sensors though. Both O2 sensor monitors have completed and the only code I have is P0420.
upstream sensor should fluctuate around 0.7v
https://carkiller.com/scottykilmer/qa/o2-sensors-sensor-1-and-sensor-2-bank-1/#post-234704
It's showing 0.315 volts on the upstream O2 sensor, I'll check it again. When I got the car, the engine harness was trash, so I replaced it with one out of another 2006 Pontiac Grand Prix.
Checked it again and at one point it went from 0.490 up to 0.760.
Looked at the guide. So far the upstream sensor seems to be working. The downstream sensor though has been reading 0.100 volts.
well as all the material suggests, sensors need to be graphed. voltage doesn't help. I have no idea what your sensors are doing.
My scanner can graph the O2 sensors. I compared my scanner graphs to the graphs in the guide and one video of graphed O2 sensors. The upstream sensor is showing a fluctuating wave and the downstream sensor is showing a steady wave. So far after comparing the graphs, the O2 sensors appear to be working showing normal waves.
can you take a photo?
yup, ill try too lol
Found it easier to just make a short video. https://youtu.be/3oiUYrDRq4E
I don't know what you mean . It looks nothing like the graphs in the literature. The upstream should be going up and down every second or less. Your downstream shouldn't be swinging wildly way up and down like that.
There's no way your data could even show this, as your tool is only updating every 5 seconds instead of many times per second. Try turning off other unnecessary live data and maybe it'll speed things up.
It's $20 software, not much to expect, the graphs could be BS. They only work if I have the live data on. Any recommendations on a scan tool? The upstream sensor is working, it's fluctuating around 0.7v. I don't know about the downstream sensor.
First link on the main page
not willing to pay for. Thanks for your help but I just couldn't see the purpose
It's the law. Don't buy a car if you aren't willing to keep it in good running order. Hopefully the $9 hack doesn't turn into a $900 ticket.
$900 ticket? Are you a lawyer? You read between the lines, its petty. Lmao
I don't understand your babble.
It's only babble cause it doesn't fit your agenda, and you give legal advice without citing facts. You hurl an insult at me, telling me not to own a car cause I didn't waste time and money on your pointless diagnostic technique. I gave you credit for helping me but you came at me more salty than a CNN reporter lol
What insult? What agenda? I gave sound advice. Who’s salty?You’re losing it , man.
Ah, typical troll response, act like nothing happened and say that I'm crazy. I don't buy your "sound advice", you can't even say where you got it from lol It's Texas, deleted trucks drive by my house everyday rattling my walls, I doubt I would get fined for a $9 hack. I would rather keep my $1,000 then spend it on a converter.
@doc your advice doesn't seem "sound" either, informing me to call a fake doctor, but maybe we should go on Dr. Phake and get famous. @mmj keep up the gifs I like it, you underestimate that I'm a Texan with a ranch of my own so thanks for the motivation lol I'm willing to settle things out but @mmj is too salty for that cause I disagree with him.
What part of FEDERAL Clean Air Act don't you understand, Tex.
Myself, I appreciate the having the privilege of driving my vehicle on public roads. It allows me to eat and pay my bills. That means keeping things legal, so I don't have to explain to my customers, that I can't finish the contract because I wanted to save a thousand bucks. That would be pretty embarrassing. I also look after my vehicle, and plan to keep it for a long time, so I keep it in the best possible condition. $1,000 is small investment for the benefits that my vehicle brings me, and if that means buying a new converter every 10 or 20 years, then that's absolutely fine with me. It's the cost of being a responsible , civilized citizen, and doing business, and I'm happy to do it.
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I also enjoy living a place with fresh clean air. You might enjoy China or Bangladesh. People there don't care about smog either.
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I am huge fan of the South. I love Texas and down to earth Southern people. You ... must have come from somewhere else.
You call people childish names and then accuse them of being salty. The lack of self awareness is cute 😉 Unfortunately for @doc, you apparently don't get jokes either.
Anyway, something seems to be eating you so I'll leave you alone now. I hope you have a better day tomorrow. Maybe take a relaxing ride through your ranch. Here's another GIF for you...
You have to find out what's going wrong upstream of the 02 sensors and CAT.
SOLUTION/ANSWER
I figured I wouldn't leave this thread unanswered so here is what I found.
The "spacer hack" by using Dorman spark plug non-foulers to move the downstream O2 sensor out of the flow of exhaust, was the very thing I didn't want to do but it turned out to be the only solution other than paying a lot for an OEM catalytic converter. It was $9 and easy to install, there are many videos on YouTube showing how its done.
The P0420 Code
P0420 95% of the time is caused by a clogged, worn out, or non existent catalytic converter. In rare cases it can be triggered by a bad O2 sensor or exhaust leak.
What I suggest before replacing any parts is to install this spacer, it will tell you right away if the catalytic converter is bad or not (P0420 will not return), and if you want to leave the problem fixed for $9, you can!
New Parts and Aftermarket Catalytic Converters:
In my case I went through and changed out the O2 sensors and catalytic converter but P0420 was still there! I was frustrated as to why with all these new parts I still had the problem. But, it turns out that the one MAJOR MISTAKE I made, was ordering a new catalytic converter without doing any research. Most would assume that any brand new catalytic converter would do the trick but aftermarket catalytic converters are not OEM spec and will still give you the P0420 code after installing. These aftermarket converters are referred to as high flow converters and even though they have a honey comb in them they will still not have enough material to meet the standard that is programmed into the ECU. So if you find out that your converter has a problem, replace it with an OEM converter from the manufacturer or take it out and try cleaning it. Don't waste your time and money with a fake catalytic converter!
Preserving The Catalytic Converter
If you don't want to see P0420 ever again, make sure your motor is running right. If it is misfiring, fix it. In my case my car was driven 700 miles, before I got it, with blown head gaskets and multiple misfire and was kept cool by water only and the radiator wasn't holding anything! It's an Oklahoma miracle that the car was even still running and didn't blow up. All that, caused the catalytic converter to go bad.
This is a hack, not a fix.
I made my point clear, and I did refer to it as a hack, I'm not denying that it's not a hack. The catalytic converter is fake, don't buy fake converters. The only thing that will fix it in my case is a real catalytic converter which I don't have and not willing to pay for. Thanks for your help but I just couldn't see the purpose of paying up for an advanced scan tool when I was able to test that the catalytic converter was not working with a $9 hack in 30 minutes.