Code P0422 and what to do about it

[x Wild Bill x]

Alright, so as some of you know from another thread, I recently got a new to me 2000 A4 and it has code P0422. Now I know this is the second 02 sensor saying that the cat is working below efficiency. I plan on replacing it, but am unsure of what to go with. I was thinking a Labree HFC and the fouler mod because I have to pass emissions here in MA. I would put on a stock cat, but I heard that Audi's don't like aftermarket ones and a stock one is expensive. Lastly, I don't want a test pipe because of the smell, this is my DD. I posted this up on a local forum and someone said that the anti-fouler mod will not work and I will still get a code with the HFC, which from reading here is un true. He also said that both oxygen sensor on the A4 are wideband and spacing out the second one messes it up, causing the car to run poorly, something also new to me. I haven't read anything about that on here, or my searching on Google, so now I don't know how to answer that. I believe you guys, who say you have a HFC and no CEL, if that is the case, I think I am going that way, unless someone has better ideas, or a stock cat they want to sell me

Thanks guys,
Bill

[Seerlah]

The guy whom gave you that information is wrong. Only the primary 02 sensor calculates A/F ratio in conjunction with the MAF. The secondary 02 sensor monitors the exhaust gas flow. Uness you have an 01 or newer A4, the primary 02 sensor is a narrow band.

As for the non-fouler mod on a test pipe. Yes, it will work. I have a Labree HFC (very well built product) and have one spark plug non-fouler on the bung. I get a CEL on occassion, but only if I drive a certain way. And I know it will pop up when I do drive like that, so I sort of anticipate it. If I had 2 non-foulers, I am sure it would not happen. But I am rather lazy to place on another one. I would recommend the Labree HFC with non-fouler (you may want to use 2). I would also suggest maybe adding an aftermarket exhaust, while you are at it. Custom built ones can be had for $300-$500 installed.

[x Wild Bill x]

Sweet Deal, exactly what I thought and what I plan on doing. Thanks for the clarification.

I plan on getting the Labree. What size non-fouler do you have on yours? And what type of driving causes the CEL? If it pops on, do you have to clear it, or will it go away if you stop driving that way. Just curious

Thanks again,
Bill

[Seerlah]

You will need to clear it yourself. My CEL just came back on a little while ago when I didn't expect it. It happens when I drive in the same gear for too long before shifting. For example, when the RPMs are monotnous for a certain period without changing and I don't change gears, then the CEL comes on. I was just doing it at around 65 mph without shifting to 5th and it happened. Wasn't expecting it that time, though. I have not scanned my car yet, but I am more than posotive that is the reason.

I am thinking about placing on a second spark plug non-fouler, but really don't feel like it. Funy thing is, it only takes a couple of minutes to do. Just follow this DIY.

[Fukenfast]

You can also try something like this...Deletes your cat with no CEL

http://www.raimotorsport.com/B5-B6-A...i-acd-0001.htm

[x Wild Bill x]

Cool, thanks guys. Quick question that I'm sure someone can answer here. When I shut the car off, all the lights go out, but when I shut the door to walk away, the mileage and stuff pop-up on the dash and stay on till you open the door again. I am assuming that this is normal and supposed to happen?

Thanks,
Bill

[Seerlah]

They go off after a little while. Then the display comes back when you open the car door.

[x Wild Bill x]

Cool, all kinds of new stuff haha, just read the easter egg thread, good stuff in there. Thanks Seerlah for answering most of my newb questions. Got another one, if a car has heated seats, does that mean it has the "cold weather package" and has the heated door handles?

Thanks,
Bill

[Seerlah]

I wouldn't know, as I don't have heated seats. But on most cars, the cold weather package includes heated seats, mirrors, etc.

[x Wild Bill x]

Got another question concerning P0422, I looked it up on the Rosstech Wiki page and they say that P0422 is caused by the oxygen sensors and not the cat. They say that code P0420 is caused by a bad cat, but a lot of people I have read say that the cat causes this code a lot more often then the 02 sensor. I just want to make sure before I order a HFC, because the rear oxygen sensor would be much easier and cheaper...

Thanks,
Bill

[Seerlah]

I get the code for low voltage on my secondary 02 sensor every now and then when I get the code. Your sensor should be just fine. You will learn that many times when you get a code for a compneent, it is moore than likely triggered by a different faulty component. Just gee the HFC and you should be just fine. But when you do the non-fouler mod, be sure not touch the tip of the sensor. And you 02 sensors and MAF should be replaced every 100k. So, if you are at that mark and still on the sensors that came from the factory, you could replace them if you like. You will increase your gas mileage while at it.

[x Wild Bill x]

Sounds good, I just wanted to double check and make sure that I'm not wasting money on the HFC. I just wish the people at Labree would have answered my email that I sent last week by now, guess I will have to call them...

Thanks,
Bill

[Seerlah]

The people at Labree are good people. They probably forgot, as we are all prone to that same default of being human. Just give them a call and they should answer any inquiry you have. FWIW, mine was $280 after shipping. Which I think is a great deal because it is a great product and they will stand by their products. If you have any issues, give them a call and they will stand by their product. Jim aka Onemoremile (the moderator of this section) had his hfc become hollow after a couple years (but he circuit tracks his vehicles, which in turn increases EGT) and they sent him a brand new unit. Actually, if you have not bought it yet you may want to contact Jim about it. I think he is trying to sell it (brand new unmounted), if he hasn't already. His user name is onemoremile, if you want to try and contact him.

[x Wild Bill x]

Cool, thanks for that tip, going to find him now :-)

Bill

[Seerlah]

I just read your other thread, and it makes sense. You may want to try and purchase an 02 sensor to see if it would go away, but I would not be surprised if it didn't and you need to replace the cat anyways. I just replaced both my 02 sensor and MAF 2 months or so ago, so I got that out of the way. My car is at 125k.

[x Wild Bill x]

yeah, I just picked up the HFC off of Jim and that comes with the spacer built in, so either way, the code should go away and I got a HFC at a good deal. I have read everywhere and no one ever said the 02 fixed it, but the cat did. One more question, can you remove the cat/dp as one unit on a 1.8t quattro 5spd? In the write up it says you can't, but I don't know if he had an tip or not, just curious so I don't fight with it for no reason, tought I read somewhere you could.

Thanks,
Bill

[Seerlah]

I had a shop install my exhaust system, so not too sure. Just use a really good amount of PB blaster on them before trying to remove the bolts. And use high temp anti-seize on the new bolts you place in (I would suggest new bolts and nuts. new gaslets are a given) and on the 02 sensor threads. Out of curiosity, how much he sell it to you for? You can PM me the price if you don't feel like posting it up. Thanks!

[getslideways]

Sounds good, I just wanted to double check and make sure that I'm not wasting money on the HFC. I just wish the people at Labree would have answered my email that I sent last week by now, guess I will have to call them...

Thanks,
Bill

just call them, they are very very nice people, but i dont think they check their email too often, it took them quite a while to reply to one of my emails so i just grabbed their number and set everything up super quickly, i think they are more "phone people" lol i got a HFC from them and couldn't be happier with the product or the service!

[x Wild Bill x]

Yeah, I plan on half a can of the PB Blaster lol, good thing is the car seems to have had a relatively easy life and the engine bay is clean so I don't think the bolts are too rusted I hope. I plan on new gaskets and hardware. I planned on calling them um tomorrow, but got a really good deal on a NIB one from a forum member. I will be sure to post the results in a week or two when I get it installed.

Thanks,
Bill

[x Wild Bill x]

Well, I got the new HFC installed and all buttoned up last week. Put the car on the road yesterday and started driving. After 40 miles or so, CEL is back on, with same code, P0422. So now I have no idea what to do, I think maybe I didn't drive the car hard enough to get the cat up to temp. I cleared the code and will try it again. I need to pass inspection in 7 days, so I need to figure this out. Also, it's a Labree HFC which has a spacer built in, so it should not be throwing that code. I need HELP!!!!

Thanks,
Bill

[seanj130]

Rear o2 sensor, I wish i had seen this thread earlier. I had that same exact code, I ended up gutting my cat and spacing the rear O2 sensor with 2 non-foulers, didnt work. I then replaced the rear O2 sensor, and I was CEL free! and with the money you saved buying it off onemoremile, you now have enough to buy a new 02 sensor!

[x Wild Bill x]

Haha yeah, I know that, I figured now it's the rear 02, umm anyway to run a test with free vag com to know for sure?

Thanks Bill

[seanj130]

actaully, im no the right guy to talk to about VAG Com, i really dont know at much about the program, i just have a handhled obd2 code reader.

[Seerlah]

You can not log which blocks that are necessary with the free version of VAG Com.

http://www.ross-tech.com/vag-com/m_blocks/030-049.html

[x Wild Bill x]

Where did all the posts from yesterday go?... :(

Bill

[x Wild Bill x]

Well, got something more interesting now, I didn't realize it the other night, but now I am getting two codes, the P0422 and also code P0140, which is oxygen sensor Bank 1 Sensor 2 faulty. So, I am assuming that I damaged the sensor when I installed the new cat, and it wouldn't surprise me. Now, I would like to know if anyone knows of a good source for a cheap 02 sensor, I can splice in a new one if I need to, or should I get my ECU edited to remove the 02 for the same price as a new rear 02? I'm just afraid that a new 02 won't fix my problem, like I have seen happen to someone else on here.

Thanks,
Bill

[Seerlah]

If you flash your ECU, you can have a code for the secondary 02 sensor delete. You clear readiness and get no CEL with. With those criterions, you should be able to pass inspection. But those codes usually go hand and foot (with a HFC/TP). You will usually recieve the cat effeciency below threshold accompanied by a faulty 02 sensor code (no signal, low voltage, etc).

I personally replaced both 02 sensors and MAF a couple months ago because it was just that time. I should not have to replace them again till I am well over the 225k mark (I am curently at 125k).

[x Wild Bill x]

Humm, I didn't realize that it would also throw a low voltage code for the oxygen sensor as well, why is that? I guess I will pick up a new rear oxygen sensor and go from there. The MAF has been replaced once already and the car only has 60K on it.

Thanks,
Bill

[Seerlah]

That code usually comes with a fluke code for the secondary 02 sensor. If it does pop up now, I just ignore it. But sometimes, the 02 code is not a fluke at all and may need attention. And I just came back from passing inspection with my car and the catalyctic converter did not pass readiness before I went in (checked via VAG Com). I needed to get it done though, as the state boys are cracking down on expired stickers on vehicles. They had a check point maybe 2 miles from my house.

[x Wild Bill x]

Thanks for that info, what state do you live in, and what kind of inspection tests do they run?

Thanks,
Bill

[Seerlah]

The emissions and inspection is all in one test. They do the OBD II scan and check for readiness. I live in NY, and we are permitted to fail one emissions component. That is why I still passed with my cat converter not passing readiness yet. Then they do the visual inspection which includes, horn, lights (brake, hazards, turn signals, low beam, high beam, reverse lights, license plate lights, etc), visual inspection of the cat converter (they just need to see that it exists), tire tread, brakes, and I think that is about it.

[x Wild Bill x]

Humm, interesting, sounds just like MA inspection, I just have to check about allowing one failure and if the cat can fail, as I know my boss' truck just failed for a bad evap purge valve. I have to look into it more, if I can pass with 5 out of 6, then I am good to go. Did you have the P0140 code also, when you passed?

Thanks,
Bill