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Old 12-22-2010, 09:37 AM   #1
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Default P0420 NIGHTMARE!!!!

P0420 NIGHTMARE!!!!
I have no other ideas on where to go with this. I practically changed every part that has to do with this damn code and have not received any type of relief. I mean granted I thank this website and everyone’s input to getting rid of this code, but still cant get it to go away. I don’t want to take it to the dealer because it would cost me a fortune and believe it or not im under budget from taking it to the damn audi dealership and having them charge me 180.00 as a diagnostic fee. So after doing long time research on this code on the internet, I have replaced the following:
Both o2 sensors
Spark plugs
Spark plug wires (Thank you audi for the recall on the wires)
Spark plug coils
Vacuum tube toward the rear of the engine that I found cracked.
Cat converter

I left the Cat for last since it was the most expensive part to replace and I broke down and went with the repair only to find out that a couple days later “Ding” f-in engine light comes back on to give me the same code – p0420 (Autozone reading). Damn this code right to hell!!! I also read on the possible outcomes that this code can be tripped by a leak in the intake, is there a way that I could possibly detect that? I would like to take pride and be able to fix my own car, hence the other reason why I didn’t want to take it into the stealership. I have a 2002 Audi A4 1.8T for those that might have a further solution. Im on my last leg here on trying to figure this out and im about to punch my dash if I see this check engine light any LONGER!! Lol. Can someone throw me a bone here.

Respectfully, Pissed off Audi owner.

Note: I don’t think I’ve gone more than a month without this engine light going off. Next car = NOT AN AUDI!!
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Old 12-23-2010, 03:09 PM   #2
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http://www.obd-codes.com/p0420 - read...

On the bright side, you performed alot of good maintainance.

Since you replaced your cat, I would try looking further up on the exhaust system. Maybe a leaking exhause manifold. Or a malfunctioning engine coolant temp sensor?

I haven't had any experience with this code, but it sounds like you replaced most of the big stuff, so I would start looking at the smaller things.
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Old 02-21-2011, 06:09 AM   #3
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Well after months of battling this “p0420” code I FINALLY found a solution to get rid of the check engine light after replacing part after part associated with this code. I was about to give up and hand over 1400.00+ to the Audi dealership until I ran across one more solution. I started reading on information concerning an O2 spacer for the second bank. This spacer I guess, gives the O2 sensor a gap so that the temperature coming out of the aftermarket catalytic converter reads within limits and “poof” engine light be gone!!! So once again I have to thank this site on saving me about $700.00 and some change. Took me a little to figure this one out, but the cat was initially on the quits. So if you guys are on the same troubleshooting boat with this code and you have done EVERYTHING in its power, give the O2 spacer a try. I bought it for 23 bucks off a german parts website. Now awaiting my next check engine light troubleshooting issue…lol.
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Old 04-26-2011, 03:11 PM   #4
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Quote:
Originally Posted by infamous107 View Post
Well after months of battling this “p0420” code I FINALLY found a solution to get rid of the check engine light after replacing part after part associated with this code. I was about to give up and hand over 1400.00+ to the Audi dealership until I ran across one more solution. I started reading on information concerning an O2 spacer for the second bank. This spacer I guess, gives the O2 sensor a gap so that the temperature coming out of the aftermarket catalytic converter reads within limits and “poof” engine light be gone!!! So once again I have to thank this site on saving me about $700.00 and some change. Took me a little to figure this one out, but the cat was initially on the quits. So if you guys are on the same troubleshooting boat with this code and you have done EVERYTHING in its power, give the O2 spacer a try. I bought it for 23 bucks off a german parts website. Now awaiting my next check engine light troubleshooting issue…lol.
Hey bro.

I'm having the same damn problem. Changed everything and still the same problem. Can you please email me the link with the part number to: monty007@shaw.ca I love this car but this is driving me absolutely crazy!!!!

Thanks in advance!!

EJ
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Old 04-28-2011, 04:04 AM   #5
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EJ,

Don’t even bother spending your money on the spacer. This solution went well for about a month and the p0420 code showed its ugly face again. I’m on the same boat as you as to driving this car off a cliff, but then again it’s paid off so I guess I’ll deal with the light. So what I did was I took it to where I had the cat put in and they ran a test on the whole emission system and they said they had no idea what was wrong since it looked like everything ran fine. So I went onto advancedautoparts.com and looked up a coupon code and got a code reader / eraser for 33 bucks and have it in my passenger seat pocket. I erase the code drive for about a week then it comes back on, so then I just erase it again for the convenience of not looking at that damn thing on my dash. It also gives me the comfort that it’s still JUST the p0420 code. I took it up to the Audi dealership to find out if they could diagnose it and they actually diagnosed it for free (What a shocker!!!). But they told me that it was the cat and they wanted twice what I originally paid for a new cat. So I told them where they could shove that cat. But anyway, I’m still looking for a solution since I’ve changed everything that had to do with that code and still get the check engine light. The only thing that I haven’t done was get the ECM flashed so that the new cat reads within tolerance (which I believe is the only thing left to do). But I don’t really want to spend 400.00 plus to have Audi do 10 min of work. So I just reset the code every time it comes up. $33.00 bucks on a code reader and I could use it on the wife’s car too if I have any problems. But I’ll tell you what, since I’ve owned the car I haven’t gone a month without that engine light coming on. So I’ll just wait till this thing blows up and then NEVER look in Audi’s direction AGAIN…. BMW here I come!
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Old 01-02-2012, 05:18 AM   #6
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Default Problem solved so far.

So I finally found a solution for this p0420 code that has been on my dash for almost a year. To recap I had a cat converter code go off, I replaced everything associated with this code to include the cat, o2 sensors, coolant sensor, cleaned the maf sensor, new head gasket, spark plugs, coil packs, etc. My last resort was to reflash the ECM at the Audi dealership. I went there and just requested the flash, which was about 180 bucks and a hour and a half on the labor. NO MORE check engine light for the past two weeks!!!! Hopefully it stays this way and I don't have anymore issues and my car seems to be running alot smoother.
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Old 01-10-2012, 05:42 AM   #7
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do you mean reset adaption values when you say reflash?
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Old 01-11-2012, 05:15 PM   #8
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Default PO420 code

I did not see your mileage in the postings, but this may apply...You may be covered under 8 years or 80,000 miles (EPA’s Federal Emissions Law of 1995)if your CAT failed. I don't know what recourse is available to you now - but worth investigating. I had CAT replaced for free at Audi, but had to "remind" them of this coverage. I rack up a lot of miles each year so this was done a few years ago on my car - had it done at 79,000 miles. Also, I am not original owner of car - this does not matter under coverage.
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Old 01-12-2012, 05:18 PM   #9
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funny i saw this, started reading, was going to say there is a software update for too sensitive of converter failure codes. But i see you went to the dealer and had it done
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Old 01-16-2012, 04:09 AM   #10
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Outback,

I dont know the specifics behind what software that Audi had used, but i just let them know that i had changed the Cat converter and needed a reflash. They took care of the rest. I assume that they knew what i needed done as far as the reflash went.
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Old 01-16-2012, 04:09 AM
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0420, 18l, 18t, 2001, 2002, 30, a4, audi, code, finally, fix, found, p0420, po420, reason, tt, vacuum


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