Code: p0420???

[CuseBora]

yep, i was waiting for it. I put the 3" TB back on and not 500 miles later does the check engine light come back on. The code is p0420. I read that it means catalyst efficiency "below threshold" in bank 1. I beleive bank 1 is my downpipe? does any one have any sort of idea what this means?

btw: the exhaust is a 3"dp to high flow cat, and 3" custom catback with a flow through muffler. both O2 sensors are plugged in.


any suggestions would be GREATLY appreciated.

[VWTUNING]

Do you have a CAT? Is it high-flow? Might need to recess the second O2 sensor so it gets less exhaust and therefor thinks the cat is working great ;)

[CuseBora]

Do you have a CAT? Is it high-flow? Might need to recess the second O2 sensor so it gets less exhaust and therefor thinks the cat is working great ;)

yes i have a high flow cat, and both of the O2 sensors are plugged in before the catalytic converter. Pete, by recess do you mean remove, or relocate?

[VWTUNING]

your second O2 sensor should be behind the cat, that is likely the cause of your CEL.

[CuseBora]

on the stock exhaust, both sensors are infront of the cat. so im lost.

[VWTUNING]

you sure? the purpose of the second O2 sensor is to make sure the cat is working - cant do that if its infront :confused:

[CuseBora]

yeah man for sure, its like right on the very front of the cat, not behind, and the wire that its on wouldnt be long enough to reach to the back of the cat

[VWTUNING]

man MK4's are wierd! :p

[CuseBora]

yeah and im sick of em'... :rolleyes:

[RichB]

Can't be right (o2 sensor locations) ..... One O2 is pre cat and the other is post cat. What kind of downpipe is this????

What motor??? 2.0L AEG, right??? Or is it a 1.8T??? The Bentley clearly shows pre-cat and post cat O2 sensors for the 2.0... on some exhuast set-ups the pre-cat one is mounted up near/on the exhust mani. If its a 1.8T, definetely two... one pre-cat and one post cat... my stock and GHL downpipe are this way.

[Master_Shake]

I hope it's a 1.8T sine he said turbo back and like Rich said all OBD2 cars have one O2 sensor pre-cat and one post cat to check the efficiency. and you should be able to solve the problem with what pete said by spacing the post cat O2 sensor so it sees less exhaust. search the tex for that topic there should be something on there about it.

[crew219]

which exhaust / DP system are you running?

Something doesn't sound right.

BTW, if you go REVO SII, you won't have to worry about emissions CELs.

Dave

[boostin20v]

Code:
SAE V.A.G

P0420 16804 Catalyst System, Bank1, Efficiency Below Threshold



Check:
- Check oxygen sensor and oxygen sensor control before catalyst http://esis.infofoundry.com:8080/vw/icons/arrowdblright.gif Page 24-103 (http://esis.infofoundry.com:8080/vw/servlet/ESIS?action=Goto&id=VW.A4.FU05.24.3.103&type=repair)
- Check oxygen sensor and oxygen sensor control after catalyst http://esis.infofoundry.com:8080/vw/icons/arrowdblright.gif Page 24-110 (http://esis.infofoundry.com:8080/vw/servlet/ESIS?action=Goto&id=VW.A4.FU05.24.3.110&type=repair)
- Oxygen sensor aging before catalyst, checking: Engine code AWP http://esis.infofoundry.com:8080/vw/icons/arrowdblright.gif Page 24-119 (http://esis.infofoundry.com:8080/vw/servlet/ESIS?action=Goto&id=VW.A4.FU05.24.3.119&type=repair) ; Engine code AWW http://esis.infofoundry.com:8080/vw/icons/arrowdblright.gif Page 24-122 (http://esis.infofoundry.com:8080/vw/servlet/ESIS?action=Goto&id=VW.A4.FU05.24.3.122&type=repair)

[CuseBora]

here is a picture of my stock exhaust, as you can see there is one O2 bung in front of the cat, and the second one looks to be about 1/4 of the way into the cat, but its definatly not after the cat.

http://uploader.ws/upload/200608/downpipe.jpg

btw: thanks for all the input!

[crew219]

how does showing a pic of the stock catback help? That's not what you're currently running.

I hope you know that most HFCs do not clean emissions as well as the stock cat so low cat efficiency codes are expected. The only HFC that works as well as the OE is the HJS 200 with the emitec core. Certain cats will "pass" but there are always situations where it will trigger the emissions code.

You have 2 options, try the spacer mod or get a chip that fakes the secondary o2 signal (revo and maybe APR).

Dave

[CuseBora]

i posted the stock catback to show that im not an idiot and that it had no O2 sensor after the cat, and my 3 inch setup that im currently running also has the 02 sensors in relatively the same spots. and im already running GIAC softwear, so no need to switch, ill just live with the light. The only reason i was asking anyways was to make sure i wasnt doing any sort of considerable damage to my car.

[crew219]

i posted the stock catback to show that im not an idiot and that it had no O2 sensor after the cat, and my 3 inch setup that im currently running also has the 02 sensors in relatively the same spots. and im already running GIAC softwear, so no need to switch, ill just live with the light. The only reason i was asking anyways was to make sure i wasnt doing any sort of considerable damage to my car.

what downpipe are you running? It sounds like a crappy design.

APR 3" secondary after the cat . . .

http://goapr.com/VW/products/images/exhaust_golf_3indp.jpg

Techtonics 2.5" secondary after the cat . . .

http://techtonicstuning.com/images/parts/251.234.jpg

GHL 3" secondary after the cat . . .

http://namotorsports.net/images/GHLDP3.jpg

Can also try welding a new o2 bung post-cat and extending the wiring. Just cap off the old o2 bung.

Dave

[VWTUNING]

I think Matt on here can hook you up with a spacer that will make the O2 sensor sit further back in the hole and there for read less gas. Thsi makes the ECU think the cat is working great ;) then you wont throw a code.

I dont think you are hurting performance right now, but you wont pass inspection like that.

[CuseBora]

well my DP is one of those ebay guys, i didnt feel like wasting $ if i didnt need to, the dp has the 1st bung right where the stock one sits, and it came with this little section with a bung for deleting the cat, but i decided i wanted to go with one, so therefore i welded the cat on after the bung. As long as its not hurting the car i dont care, i already got my yellow inspection sticker...

[VWTUNING]

yeah but what about next year? and what happens if you get a ligitimate CEL? you wont know cause its already on...


just my 2 cents :)

[crew219]

yeah but what about next year? and what happens if you get a ligitimate CEL? you wont know cause its already on...


just my 2 cents :)

+1

Dave

[CuseBora]

yeah you have a good point, i guess ill deal with it when i have $1200 extra dollars to spend on a non "crappy design" exhaust...:rolleyes:

[RichB]

My 1.8T stock downpipe is the exactly the same as the one you pictured. I think the 2n'd O2 sensor is positioned after the CAT... its probably built such that the CAT is physically in the enlarged section before the 2nd O2 sensor and the even larger chamber that the 2nd o2 sensor is mounted into is probably there for some technical reason (like to allow the CAT to operate more efficently or something like that) and there is nothing inside the section of the stock CAT.

As others said, putting on a spacer to back out the rear o2 sensor somewhat out of the exhuast gas flow will most likely take care of the CAT low efficiency code or even bring it down to a intermittant code (which won't set off your CEL and allow you to pass future inspections). This is a fiarly common thing on chipped cars with high flow cats.

Would be interesting to see a pic of how you how have things set-up (not sure I understand from your description were the 2nd o2 sensor wound up). BTW, What is the 3" DP mated to??? Stock Cat back or a 2.5" or 3" CAT Back? Hows the noise level??? Car must really rev nicely/freely up top now! :) How is your GIAC chip taking to the bigger DP???

As to the concerns about missing that CAT eff code... With VAG-GOM there are other ways to monitor the health of the CAT... I don't see this as being a big problem.

[crew219]

As to the concerns about missing that CAT eff code... With VAG-GOM there are other ways to monitor the health of the CAT... I don't see this as being a big problem.

Can't monitor the cat at all given that his secondary o2 is in front of the cat. Pete and I were just saying that it is bad to have a CEL on all the time because you don't know if something else has gone wrong to trigger the code.

Dave

[CuseBora]

Would be interesting to see a pic of how you how have things set-up (not sure I understand from your description were the 2nd o2 sensor wound up). BTW, What is the 3" DP mated to??? Stock Cat back or a 2.5" or 3" CAT Back? Hows the noise level??? Car must really rev nicely/freely up top now! :) How is your GIAC chip taking to the bigger DP??

After the downpipe i used a small section of the race pipe (cat deleter) for the bung that it had, i guess that was my mistake, by looking at my stock DP i thought that both sensors would be better infront of the cat. After the cat its a non resonated custom 3" all the way to the back bumper. Its running awesome now, the turbo spools so much faster, and it keeps pulling hard about 5grand now. the noise level isnt too bad either for being non resonated, i mean it is a bit loud, but it doesnt have that horrible drone on the highway.

thanks for the input Rich!

[RichB]

After the downpipe i used a small section of the race pipe (cat deleter) for the bung that it had, i guess that was my mistake, by looking at my stock DP i thought that both sensors would be better infront of the cat.

Ahh... 20/20 hindsight....MKIV weirdness strikes again.... you can always fix the location of the 2nd O2 Sensor later. :) BTW, if you ever run into anything down the road that you may not be sure about, I have the latest MKIV Bizzentley and 2005 European ETKA that I can look things up for you. Feel free to PM me if you need to.

After the cat its a non resonated custom 3" all the way to the back bumper. Its running awesome now, the turbo spools so much faster, and it keeps pulling hard about 5grand now. the noise level isnt too bad either for being non resonated, i mean it is a bit loud, but it doesnt have that horrible drone on the highway.


Sweeet... You may want to try the ECS lighweight/underdrive pullies which will frees up a several more HP up top and lets the motor rev a bit more freely.... or .... next step: bigger turbo! :p :)