DTC P0420 - No Driveability Issues

[Sublimewind]

I could believe this..^^^ I've have MAF problems with my other car a lot... But I was also told that I could throw that code because I removed a lot of heat shielding from the exhaust, after it started rattling.. they said on long drives at higher speeds I could cool the exhaust enough for the O2 sensor to read wonky.. Mind you my manifold on my other car is UNDER the car, not behind/in front of the motor.. so it's right in the air stream..

[joatmon]

Quote, originally posted by csvibe »I had a code 0420 on my 2003 vibe in april 2008. the converter was replaced the code went away and it passed the NY state inspection.Two weeks later the MIL light is back on. The car runs fine and gas mileage is about the same so we drive it until the inspection is due April 2009. I check the codes and it is the 0420 again. I send the car back to my buddy's garage where the converter was replaced last year. He does some research and talks to a friend of his at a Pontiac dealer. They say the mass air flow sensor causes the problem, it gets a little dirty and runs the fuel just a little too rich and fouls the converter and then code 0420 sets. He put a new MAF sensor in and ran the car to clear out the converter, that didn't work so he had to replace the converter (good news his supplier warranteed the year old converter). Bottom line is we have more than 6,000 miles on the new converter and the MAF sensor wirh no codes. Suggestion: Replace MAF while code 0420 is still intermittent and the converter will survive.I replaced my cat 101K miles ago and am still onthe original MAF sensor. I have cleaned the MAF a few times, but I wouldn't necessarily say that P0420 is a cat going bad from a bad MAF, and that replacing the MAF would save the cat. Otherwise, my second cat would have gone bad a long time ago.

[EddieandtheVIBE]

I have an 03 AWD. I began seeing the code @ ~75K miles in late 2007. Replaced both O2 sensors, no change. Took it 2 dealer, they replaced cat. All was good!About a week ago, @ ~ 105K miles, CEL re-appeared. Checked code, same one!!It couldn't b the sensors or the cat again after only ~ 30k miles, could it?I've read about changing the plugs. I haven't done that yet, so I'll try that 1st and c what happens......

[joatmon]

It's ba-ack again on 7/1/2010getting it quite regularly now - 1/21/2011

Attached files

[fss106]

My P0420 story started 2 years ago. (90k miles) I drove 30,000 miles cross country. CEL would come on sporadically, I'd sleep in a hotel, when I woke up in the morning I'd keep my fingers crossed that the light would be out. Sometimes it would, sometimes it wouldn't. Had it checked once during an oil change. "P0420." Didn't come back on again until I got home for the summer (120k miles). So now its about a year a half later. CEL hasn't gone off for 4 months (135k miles). Had it checked twice more during oil changes. Both times came back as P0420. Found a converter this weekend for $215 at Napa. Found this thread 24 hours later and am going to get the spark plugs changed this week. (Haven't changed them since I bought the car in 2006). Hey its been a trying economy.... Will try the converter after that.... Updates to follow.

[fss106]

Replaced all four spark plugs this afternoon. My first ever spark plug replacement endeavor, on this or any other car. Relatively easy apart from the fear that every single one I replaced I was cross-threading. I have this feeling I cross-threaded at least one... It's really a blind sort of installation. And I didn't have a torque wrench so I have no idea if I tightened them enough, or too much... but I fired up the engine, and got out on the highway and floored it. Which, in the past, would have triggered my CEL... so far nothing though. Any words of wisdom would be appreciated however before I drive too long on a bunch of spark plugs that may or may not be cross-threaded....

[fss106]

so being totally impatient for a reply I went out and removed all the spark plugs again. had not cross-threaded any of them-- when i put them back in this time is jammed a piece of rubber hose on the end of them and lowered them down into the hole. i threaded about the first 3/4 of the spark plug using the hose figuring if it started grabbing the hose would slide. think i nailed it-- took me about 1/10 the amount of time it took me to put them in the first time too

[star_deceiver]

After a few days of driving, take your wrench to the plugs again and see if any came loose if you're unsure.

[fss106]

CEL light is back after two days.... so I guess I'll take it to the dealer, see what's next-- o2 sensors or cat... it was a nice try.

[fss106]

cleaned the MAF sensor a day before taking it to the dealer to get the CEL checked. that was dumb. unplugged the battery and cleared the CEL. gonna have to take it back down in a week or two to get it looked at again. Tried to drive it as hard as possible on my way to the dealer. No luck. The light ended up coming back on two minutes before I pulled into my driveway.

[fss106]

So, after just replacing the A/C clutch on the compressor and driving for 3 days my CEL cleared. And-- its been off for 4 days now... No battery disconnect, no, nothing-- So I'm thinking one of 2 things. (1.) The light just got sick of trying to tell me something, gave up, or burned out.... or (2.) When I replaced the A/C clutch I also put on a new serpentine belt (something I haven't done since the light originally came on) and that fixed it.... granted I can't imagine that would do it, or why that would work... I've heard the CEL is supposed to go off after 2 successful driving cycles so I'm really optimistic at this point, but then again, if I wanted to test the bulb to see if it burned out how would I go about doing that?

[fss106]

CEL comes on when I turn the ignition, goes off-- so everythings in order there. guess its just my lucky day

[Empire1300]

07 Vibe with 44,300 mi. Got a CEL today and code is P0420. Reading all of these posts and other threads does not make me happy.... Has anyone had this code under 50,000 mi?Anyone with experience going to dealer and getting warranty covered service? I will be irate if I have to shell out $500 or more.Does a new cat fix it?Also- took my car to Michel Tires Plus to get CEL diagnosed. They want $100. Sounds ridiculous to me. Everyone else pulls codes for free, right?

[RIT]

I got that Code at about 70K miles, and brought it to the dealer, and he replaced the Cat under warranty, and it cleared the Code. I may have had to pay a minimal (Go For It !!!

[EddieandtheVIBE]

I tried replacing the plugs, but the code came back. I tried cleaning the MAF, code re-appeared. A friend of mine looked over my vibe and said that he heard a clicking noise coming from the MAF?? (aside from any standard engine noises) Anyone else experience this? I'm nearly out of time as my inspection is up soon, so I have to get the code cleared. I've bought another pair of 02 sensors, but haven't installed them, jic the prob is the cat or the MAF and not the sensors (so i can return them!). Right now the vibe is at a repair shop and they are advocating a cat replacement, but they say they are having trouble locating a replacement. I've been able to find aftermarket ones online, so not sure why they can't.

[joatmon]

getting a P0420 regularly now, not happy about having to replace it again

[ColonelPanic]

How many miles are you at now, joat? Sorry to hear it's happening again.

[joatmon]

Quote, originally posted by ColonelPanic »How many miles are you at now, joat? Sorry to hear it's happening again. 266K miles. Its been getting progressively worse for some time. I took it off the car this weekend and cleaned off a crusty white layer that was obstructing the cat intake and my flow test (with a leaf blower) showed its flowing well. Supposedly ethanol in gas can wash oil additives that coat the cat and my cars tendency to consume oil also can't help. Last time I got an OEM cat from a dealer. GM still sells them about half the cost that Toyota charges. This time I might just take it to an exhaust shop. Or at least get an estimate from one for a nonOEM cat.

[Piggy]

I'm sure you know this but I thought I'd bring it up; The older 1zzfe engine had a problem with either the valves or the piston rings (pretty sure the rings), such that oil would seep into (I believe, been some time since I read about this) the intake. Now, I don't know how much, if any of what I've said makes sense to anyone, but my 99 Corolla had the issue. I was always loosing oil but never any smoke. I suppose it could have been the timing chain o-ring but I never saw oil on the side of the engine. My point with this being, are you sure it's being burned off and not seeping into the intake?Out of curiosity, at what mileage did you first replace you cat? I just had a Walker installed @ 214,XXX and feel nervous that if I keep the car it'll need another soon... (40,000 miles in a year and a half) On the positive my 420 is off and has stayed off for over 1000. And just a side question, are there any stations where you can get ethanol free gas?

[ron_estacio]

I've been getting the P0420 code on and off for a month now... trying to figure things out...
2005 Vibe w/ 200,000+ miles on it.
I think I have noticed some correlation with when I get gas; but the first order of business is some bonding time with my dad changing spark plugs... I don't think I can afford to bring it to the shop. Cost of living in San Diego is too high and my pay is too low. Anyways here's hoping I don't kill the car & my income. Links to relevant threads & tutorials would be much appreciated.

[Salsa Guy]

Sorry to say but there's an 85% chance your CAT is bad. You can try to replace the O2 sensors but more than likely it will be a waste of money. You could try the O2 extender on the rear ($10) and that may get you by for awhile. But I believe it's illegal in Cali. If you get caught it would cost you more than just replacing the CAT.

[ron_estacio]

Thanks for the quick reply SalsaGuy. I've been getting the same advice regarding (not-legal) workarounds: it can very easily end up with me getting a new Cat on top of the cost of the work-around (& fine)...

[Salsa Guy]

O2 sensors may not be a bad idea considering the miles. A bad CAT eventually can cause major issues including engine failure.

[Murdoc]

At 147,000 miles the dreaded CEL came back on my 2003 pontiac vibe base model with autozone reading the code as p0420 telling me i need a new cat converter. I said impossible i had one put on 2 years ago, plus i changed the manifold intake gasket. So i cleared the code by unhooking the the battery for 30 min. 319 miles later CEL back on. So with inspecton due at the end of January, i dump 2 cans of a product called seafoam in the gas tank plus put higher octane gas in and reset CEL by pulling the battery. After 2000 plus miles later NO CEL has returned PLUS it passed inspection/emissions. I'm confused now but I'm glad it hasn't returned. Also no gas mileage difference no driveabilty issue while check engine light is on. My PCV valve was gunked up oily and sluged i cleaned that and put it back in.

[Salsa Guy]

Yea I got a P0420 last night. I cleared it and plan on replacing some O2s then do the CAT down the road.

[Reaccion]

I had the same code and I solved the problem Maybe you want to read my post:

viewtopic.php?f=12&t=39506" onclick="window.open(this.href);return false;

[Salsa Guy]

I had the same code and I solved the problem Maybe you want to read my post:

viewtopic.php?f=12&t=39506" onclick="window.open(this.href);return false;

I'm the one who told you to do the defouler. LOL...1/2 the posts in that topic are mine. The defouler fixes nothing, it just buys time and if caught using it in some states you can be fined. I'll stick with replacing the CAT and both O2 sensors

[Reaccion]

I had the same code and I solved the problem Maybe you want to read my post:

viewtopic.php?f=12&t=39506" onclick="window.open(this.href);return false;

I'm the one who told you to do the defouler. LOL...1/2 the posts in that topic are mine. The defouler fixes nothing, it just buys time and if caught using it in some states you can be fined. I'll stick with replacing the CAT and both O2 sensors

I KNOW!!! How could I say otherwise if your posts are all there?

One defouler does not fix anything. However, have you tried two defoulers one after the other???

[cthomasparr]

I have the same issue with P0420 which seems to be coming up more and more often. I followed some advice and changed my plugs and intake manifold gasket. The car runs great now but still has the code. I won't need to go through emissions checking for another 2 years, but I wanted to consider fixing this. I currently have a 2004 base, auto trans and 208K miles.

I would like to know if anyone had somewhat longer term success changing out the cats with an aftermarket and can recommend one. Looks like most units replace both cats before the resonator, so the pipe stock must be cut and clamped. I am worried that aftermarket cats will still have MIL issues and the OEM is around $800 OUCH...

Also, other than needing to turn off the MIL, what is the downside to continuing life as normal? Could there be any possible long term side effects if the car is running great and fuel efficiency is still pretty good?

Finally... I have access to a smartphone app that tells me 02 sensor voltages. Is there any way to use these as diagnostic tools? Seems the both idle at .1V, slowing down quickly they fall to 0V, but at a steady cruise they seem to jump around .2->.7->.6??

Thanks!!

[Salsa Guy]

The O2 signal is a sine wave so the voltage is constantly changing on the DBC cars. The voltage will swing from .1 to .9 volts on the front O2 and I would expect to see .1 to .7 on the rear. The ECU wants to keep and average of .45 volts on the front and wants something less on the rear. When the voltages are similar is when it pops a P0420. So there are several things that can happen that will cause that code.
1) A bad front O2 that's reading lean but in fact the car is rich causing the rear O2 to read higher.
2) A bad rear O2 that's reading higher than it should.
3) A bad CAT.

85% of the time it's a bad CAT. However with that many miles I'd suggest replacing the O2 sensors anyway. 2 Denso O2s will cost you about $110 and 15 minutes of install time. It may fix the CEL but it could cause it to come on more often. You could try the defouler.

Any harm? If the CAT starts plugging you'll notice it in the performance and gas mileage. Then you need to deal with it directly because it will damage the engine.

On the DBW cars they switched to an AFR sensor on the front but the rear is still an O2.

[cthomasparr]

It sounds like getting those "instantaneous" O2 readings doesn't do too much for me. I did notice that they seemed to track each other more than jmy other cars that seemed very random. Maybe I can watch a little closer expecting them to be different.

I think my plan of action is to take out the two sensors and clean them with throttle body cleaner. I would have to get them out to change the cat anyway. Give me a chance to get under the car and see how healthy the rest of the exhaust pipes are. I will put them in and see how long I am code free. When it comes back I can consider doing the Cat and sensors.

Still looking for a suggestion on a replacement cat. I saw Rockauto has a Bosal for around $225. The warranty ( not sure of the details) looks like it is good for a minimum of 25K miles on emissions. Not too horrible.

[cthomasparr]

Oh forgot to ask DBW, DBC?

[Salsa Guy]

Drive by Wire, Drive By Cable. The 1zz FWD 03-04 and AWD 03-06 are DBC. 1zz FWD 05+ are DBW

[Murdoc]

well my check engine light came back on, so i guess im try and do the catalytic converter myself with the post from this forum. have to wait until the weather gets better closer to spring. so annoyed!

[Salsa Guy]

^You get a P0420?

[Murdoc]

Yeah the dreaded P0420 code returned after 3000 miles of it being off. Anyone on here try the EVAN FISCHER catalytic converter? I really don't feel like spending the $700 plus on a GM one the car has 149,000 miles for petes sake. I want to attempt to do this myself and cheap as possible.

[Rayven01]

If your two year old cat went bad already, either A) it was a cheap aftermarket cat (which are often known to not last) or B) you've got an underlying engine problem causing your cat to get overworked and go bad. If it's A, putting another cheap aftermarket cat will just kick the can down the road. If you don't plan on keeping it long I suppose it's the cheapest way out, but kind of a rotten thing to do to the next owner. If it's B.. putting in another OEM cat will kick the can down the road a little farther, but to really fix it is probably going to cost you a bundle.

[cthomasparr]

I was looking at RockAuto and they have a complany called Davico which looks like its products are made in USA, somewhere in Massachusetts. Warranty seems OK 25K on internals 50K on outside/pipes. Not sure about how easy they are to install. Cheapest option is under $200, but you have to cut OEM pipe and use resonator half. There is also a pricier model that includes both pieces. Contacting the supplier to double check warranty info and get install instructions.

[Murdoc]

Ok took it to a place who cut out out the old welded in a new he only charged me $188 realizing that this is the second time this has been done. He said the CAT CONVERTER was "fouled out" and there was awhite substance possibly he thought i burned oil, however my vibe has never smoked of burning oil. I told him this is the last time i'm doing this next time its a new car. at 152,000 miles so we will see how long this last seeing the last one only last around 2 years.

[Salsa Guy]

Have you tried replacing the O2 sensors?

[cthomasparr]

I joined others who have done the spark plug defouler trick to avoid the P0420 code. Seems to be working well as the light that was coming on weekly has not come on during a few weeks of long trips. I came really close to pulling the trigger on some Walker exhaust parts with a $100 rebate from Rock Auto, but decided to go this route instead. All things considered was a relatively easy fix.

[Reysie]

Now is Jan. 3rd 2015 , has the light come back on with P420 since you 've done the spark plug defauler?

[cthomasparr]

Hasn't come on a single time since I did that and it drives as good as always with no mpg loss

[lannvouivre]

A below-efficiency catalytic converter will not cause driveability issues unless it is plugged. It's only for emissions, not how the engine performs. However, if it was plugged, it would slow your engine's ability to rev and eventually damage it due to excessive backpressure.

The catalytic converter is a reaction plate. If it stops working well--that is, the reactions are reduced for some reason--and it works at less than 80% efficiency, the code is thrown. It's not always due to the reaction surface being dirty, hence it not always impacting driveability.