VW Beetle Forum banner
1 - 20 of 72 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter · #1 ·
Hey guys, I was driving yesterday and all of a sudden my CEL comes on. The following afternoon I go to Autozone to get the codes. Turns out it was the p0420 & the p0141 code that popped up. I've read about the 420 code and saw faulty cats, so I called my local VW dealership seeing if my cat was under warranty (after reading on here that they should be under warranty for 12 year/120,000) the man asked for my VIN and said my car was not under warranty and replacing a cat would run me $1500...I said no thanks of course. What should I do to go about fixing this problem? And is the p0141 code causing my p0420 code to pop up? Some advice would be highly appreciated! Should I replace the post-cat o2 sensor? I just replaced my pre-cat one, and i do have the part for the post-cat o2 sensor just haven't gotten around to taking it in to install it. Seems like I can't get a break with this car, hope to hear some optimism.

Thanks.
 

·
Registered
Joined
·
15,842 Posts
16804/P0420/001056 - Ross-Tech Wiki

16525/P0141/000321 - Ross-Tech Wiki

Well, it could be a number of things; based upon the 02 sensor code, it would seem that sensor (most likely) needs replaced. Be sure to replace it with a high quality oem Bosch part; you can look up the correct part here (be sure to have your engine code and get the oem non universal version of the sensor): in your case bank1sensor2 is the "downstream" 02 sensor:

https://www.boschautoparts.com/auto

To diagnose the problem; it would helpful to have a scan tool with live data, do you have access to one?


Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #3 ·
16804/P0420/001056 - Ross-Tech Wiki

16525/P0141/000321 - Ross-Tech Wiki

Well, it could be a number of things; based upon the 02 sensor code, it would seem that sensor needs replaced. Be sure to replace it with a high quality oem Bosch part; you can lol up the correct part here:

To diagnose the problem; it would helpful to have a scan tool, do you have access to one?


Sent from AutoGuide.com Free App
I did get the codes scanned by Autozone supplying me with those 2 codes. Would it be better to have it scanned by a specific VW scan tool? And would having a bad o2 sensor result in the bad cat reading? Appreciate the fast reply wanting to get this done before the weekend ends.
 

·
Registered
Joined
·
15,842 Posts
Anything is possible; I would replace the sensor and go from there. Having a scan tool with live data capability, can help you diagnose the problem more intelligently. If it is beyond your capabilities; I would seek pro help at a indie shop that specializes in Volkswagens.

By the way; what brand 02 sensors are you using as replacements? Cheap aftermarket non oem/universal 02 sensors can possibly cause problems.

Also, some members, have had success; with using Seafoam cleaning treatment to address the cat specific codes.

Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #5 ·
Anything is possible; I would replace the sensor and go from there. Having a scan tool with live data capability, can help you diagnose the problem more intelligently. If it is beyond your capabilities; I would seek pro help at a indie shop that specializes in Volkswagens.

By the way; what brand 02 sensors are you using as replacements? Cheap aftermarket non oem/universal 02 sensors can possibly cause problems.


Sent from AutoGuide.com Free App
Alright I'll go ahead and replace the sensor first and see if that gets rid of the CEL. If not indie shop it is. And I'm using Bosch o2 sensors i got on Amazon for about $80 or so. On a side not, in between gears the car has a stutter to it when shifting. I don't know if this is a separate issue or not but figure I'd bring it up.
 

·
Registered
Joined
·
15,842 Posts
When you say stutter; do you mean hesitation or a misfire?

After the 02 sensor swap (do a hard reset); if the cat code is still there, I would consider trying a Seafoam treatment first. It is not terribly expensive and it's worth a try, there are members here with success stories, doing this.


Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #7 ·
It's a hesitation and a pretty aggressive one sometimes. Usually during low speeds though, when I'm cruising on a highway doing 50+ there's never a hesitation.
 

·
Registered
Joined
·
15,842 Posts
Could be ignition related or fuel delivery issues; when was the last time a tuneup was performed on the car or the throttle body cleaned/aligned? Plugs, ignition wires and coil pack failures; are common service items, that wear out and a new fuel filter couldn't hurt either.

However, address the 02 sensor replacement; possibly a Seafoam treatment and go from there.

Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
3,690 Posts
P0420 can and often does mean a bad converter, HOWEVER, there are a lot of other things that can cause these codes. Also keep in mind with as small as a 5% reduction in converter efficiency can trigger these codes.

Replacing the post-Cat O2 sensor is not likely going to fix this problem, it may actually make it appear worse if the current sensor is a bit lazy.

Everything from exhaust leaks letting extra air/oxygen into the exhaust stream (like cracked O2 sensor bung welds to leaking exhaust gaskets to a leaking flex pipe) to a carboned up converter due to the engine running too cold and/or too rich.

Suggest you get an OBDII smart phone/tablet App for $30 or less and you can verify the engine temp and actually graph the post-Cat O2 sensors.

Get an OBDII smart phone/tablet App and interface, typically $30 or less. These Apps are usually best for driveability issues and they support Emission Readiness Monitor Status, Freeze Frame and Live/Realtime data. They are also great for Logging data for review after the car has been driven and can really help find unusual problems.

Android - Touch Scan for $5.00 and ELM327 OBDII to Bluetooth interface.

iProduct - OBD Fusion for $9.99 and ELM327 OBDII to Wifi interface.

Some people prefer to have an extension cable to keep the interface away from their feet.

Something like these cables are often of interested:

http://www.amazon.com/gp/product/B0...ue&ref_=ox_sc_act_title_1&smid=A13I33IUTGJ9BK

Amazon.com: Diageng OBDII Extension Cable, 5ft (144201): Automotive

I usually suggest getting the OBDII interfaces from Amazon if you are located in the US/North America. Make sure you choose an interface that indicates that the order will be "Fulfilled by Amazon" otherwise you may be waiting for WEEKS for an interface to arrive from Asia. Ebay is another option, but pay attention where the interface will be shipped from, again weeks for an interface from Asia, so if you can wait and want to try to save some money, go for it, but if you need an interface soon, choose wisely.

Read this thread, not a VW, but you can get a good idea as to how graphing can show questionable converters.

Aargh, failing CA smog - new cats? - E46Fanatics

Interesting read where even an "expert" CA SMOG technician is questioning me and what I can tell with a $30 smart phone App compared to his 5-6 figure SMOG test machine and dyno and I can even show if one of a multi converter system is actually a bigger problem rather an a composite of what comes out the tailpipe.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #10 ·
Could be ignition related or fuel delivery issues; when was the last time a tuneup was performed on the car or the throttle body cleaned/aligned? Plugs, ignition wires and coil pack failures; are common service items, that wear out and a new fuel filter couldn't hurt either.

However, address the 02 sensor replacement; possibly a Seafoam treatment and go from there.

Sent from AutoGuide.com Free App
We haven't tuned the car since we got it, should get on that. Also with the throttle body I haven't cleaned or aligned it either. I'll look into all that because the hesitation is getting worse. I'll update with the whole CEL situation as I get these things done, thanks again for the input really helped out.
 

·
Registered
Joined
·
3,690 Posts
We haven't tuned the car since we got it, should get on that. Also with the throttle body I haven't cleaned or aligned it either. I'll look into all that because the hesitation is getting worse. I'll update with the whole CEL situation as I get these things done, thanks again for the input really helped out.
Spark plugs are the primary thing that is a consumable and should be replaced at a specified interval. I typically try to do this around 50k miles as the platinum plugs have a longer lifespan. Some platinum plug manufacturers claim 100k miles as I recall, however, I would never run then this long.

40-50k is not a bad interval to replace spark plugs.

Not sure I would get excited about the throttle body at this point. Get the engine temp, Fuel Trim and any codes and Freeze Frame info.

Then go from there.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #12 ·
Spark plugs are the primary thing that is a consumable and should be replaced at a specified interval. I typically try to do this around 50k miles as the platinum plugs have a longer lifespan. Some platinum plug manufacturers claim 100k miles as I recall, however, I would never run then this long.

40-50k is not a bad interval to replace spark plugs.

Not sure I would get excited about the throttle body at this point. Get the engine temp, Fuel Trim and any codes and Freeze Frame info.

Then go from there.
We actually just did the sparks about a month ago and the ones we replaced were completely done. But that still didn't solve my hesitation issue. It's a pretty hard jerk in between gears, so I'm not sure what can be causing that. For now, I am taking it to a shop first thing in the morning to replace the post-cat o2 sensor. I was forced to take it to the shop for my pre-cat o2 sensors after a failed attempt replacing it with a help from a friend. The bolt to the sensor wouldn't budge, they had to take a pretty large torch to it to remove the bolt.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #13 ·
Update:

We just got the o2 sensor replaced this morning & the place cleared the codes. Hoping this resolved whatever was wrong with that p0420 code. Will update if any CEL does come about after having the o2 sensor replaced & codes cleared.
 

·
Registered
Joined
·
3,690 Posts
Do not mean to be a doubting Thomas, but your P0420 WILL be back.

If you have not purchased a smart phone/tablet App and interface, get it now, you WILL need to learn how to use it and you may be able to "Manage" the P0420 codes.
 

·
Registered
Joined
·
2,545 Posts
code p0420

I too had the dreaded P0420 code problem a few years back and several folks told me to the change the CAT , change the O2's but I was hesitant and never did change those parts. Then I got it fixed and problem has not reared it's ugly head again for the last two years. glad I never did change those parts.
 

·
Registered
Joined
·
2,545 Posts
420

esse10, so, you replaced the both 02 sensors and using Seafoam; through the throttle body, did the trick for you?
shaky topic that Seafoam............some folks don't believe in that "wondrous fuel of the GODS." LOL :p It's been two/three years ago for me to remember billimade, but I know I was getting ready to replace the CAT but decided to try the seafoam job and that wind up fixing it for me, haven't seen that dreaded P0420 in two years now. Now I do the seafoam cleaning annually. Car runs a lot smoother now.

It was a no Brainer decision, Pay $8 bucks for a can of seafoam or pay 300 for a new CAT.
 

·
Registered
Joined
·
18 Posts
Discussion Starter · #18 ·
shaky topic that Seafoam............some folks don't believe in that "wondrous fuel of the GODS." LOL :p It's been two/three years ago for me to remember billimade, but I know I was getting ready to replace the CAT but decided to try the seafoam job and that wind up fixing it for me, haven't seen that dreaded P0420 in two years now. Now I do the seafoam cleaning annually. Car runs a lot smoother now.

It was a no Brainer decision, Pay $8 bucks for a can of seafoam or pay 300 for a new CAT.
I'll have to go the seafoam route and hope this CEL doesn't pop up again. Called my local VW on a quote for a new CAT and they said $1500 :confused: seafoam shall do for now lol
 

·
Registered
Joined
·
2,545 Posts
p0420

I'll have to go the seafoam route and hope this CEL doesn't pop up again. Called my local VW on a quote for a new CAT and they said $1500 :confused: seafoam shall do for now lol
Just remember to only let it suck a little at a time using a tapered clear hose. The ECM will throw a few codes at first when you do this cleaning but those will eventually clear later after you run the car for a while. There is a really cool utube video of someone doing a VW jetta you might want to google that before you do yours.
 

·
Registered
Joined
·
105 Posts
I am also having this p0420 error coming, replacing the spark plugs didn't help. I used Cataclean twice with no success. I am going to try the Seafoam thing, and if it doesn't work. I will try to replace the upstream o2 sensor, and if it doesn't work, the downstream.

Can you tell me how to use the Seafoam?
 
1 - 20 of 72 Posts
Top