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snicknc 08-26-2010 02:20 PM

P0421 Code
 
Hi,

I just picked up an 02 Vue 3.0L that popped the SES light literally driving it home after I signed the title-- fun stuff

This code caused me to fail the emissions part of my safety check.

After a lot of googling and searching the forums here, I can't seem to find anyone else that just has this one code. It seems like it's usually paired up with 0431 or a specific O2 sensor code.

My plugs were replaced about 20k miles ago by the previous owner at a dealership.

With just this code popping up, is it probably that post-cat O2 sensor on the front, or the cat itself?

Chazberry 08-26-2010 04:59 PM

Re: P0421 Code
 
[QUOTE=snicknc;1653518]With just this code popping up, is it probably that post-cat O2 sensor on the front, or the cat itself?[/QUOTE]

This is a good read even if it isn't a good fix . . .
[url]http://www.club3g.com/forum/performance/55284-how-fix-ses-error-code-p0421-about-5-bucks.html[/url]

snicknc 08-26-2010 05:04 PM

Re: P0421 Code
 
It's worth a shot-- I'll try it and report back. I'm going to check those O2 sensors as well.

Thanks!

Routs 08-27-2010 11:22 AM

Re: P0421 Code
 
Ironically I had P0431 (the same code you got, only for bank 2) go on me about 25 kms after leaving the dealership where I bought it. I promptly returned and asked for some clarification on what they would do. Their garage was packed so I couldn't get in at the moment and couldn't leave the truck for an extended period of time.

The initial response from the Service Agents was that I must have filled the truck while it was running or that I must have left the gas cap off. After I politely told them to eff off because this wasn't my first "rodeo" they gave me some other solutions.

Apparently if the gas is somewhat poor or has been sitting for a while, it can sometimes give the cat issues leading to this code. They also stated that if it had sat for a while, there may be something stuck to the sensor. I then left and cleared the code at home. I added a fuel injector cleaner to my tank and hit the highway for some "spirited" driving.

The code did come back but only for a short while and then went off again. It hasn't been back on for at least two weeks now.

snicknc 08-27-2010 12:02 PM

Re: P0421 Code
 
That's an interesting point. The light came on shortly after my wife put gas in it driving home from the folks we bought it from. I don't think we've gassed it up since then, so it could be bad gas. It also slung the evap canister (aka gas cap loose) code, but that cleared up when I cleared the codes a couple of times.

I'll go ahead and try this non fouler trick, gas it up and drive it an hour or so to get the ready code.

Hopefully I can pass the emissions this weekend to get this thing registered and then finish up with the rest of the maintenance I'm wanting to do.

snicknc 08-28-2010 01:08 AM

Re: P0421 Code
 
Alright, so I pulled both bank 1 O2 sensors. The pre-cat sensor looked normal. The post-cat sensor had a dark ring (I'm guessing carbon) around the base and a grey-white stripe going from the base over the tip and down the other side.

So maybe some non-sensor safe RTV at some point poisoned it, in addition to running a little rich? I don't think it's still running rich, as I roughly calculated my gas mileage during the 100 miles to be around 23-25 at highway speeds.

It doesn't look like water contamination, as the white is just limited to that one stripe, but I'll probably do a compression check tomorrow just to make sure the head gaskets are good.

I swapped that sensor out with a new OEM one and drove it 100 miles, turning the engine off and starting it back up a couple of times, making turns, braking, etc. No SES light, so that's good I reckon.

At this point, I'm hoping I drove enough to get that "ready" code so I can slam this thing through emissions and get it registered.

For those interested in the non-fouler trick, be aware that it looks like our stock sensors are wider than 1/2", so you'll probably have to use a universal sensor. I couldn't get the sensor to fit in the fouler. I'll throw the picture of my bad sensor on here at some point this weekend just for thoroughness.

To be honest, I'll probably wind up just picking up two universal sensors as well and using the non fouler on both post-cat sensors as I'm honestly pretty aggravated that I'm failing the safety check for f'ing emissions-- especially something as dumb as this code. Over half the counties in NC don't require emissions, but mine does-- lucky me :)

Thanks for the help so far guys.

snicknc 08-28-2010 12:02 PM

Re: P0421 Code
 
Well, still got a not ready code on the cat. Took it back out to drive some more and the SES light came back on-- P0421.

I guess I'll be picking up a universal sensor to do the no-fouler trick to pass this inspection.

far2grumpy 08-28-2010 05:57 PM

Re: P0421 Code
 
[QUOTE=snicknc;1654175]Well, still got a not ready code on the cat. Took it back out to drive some more and the SES light came back on-- P0421.

I guess I'll be picking up a universal sensor to do the no-fouler trick to pass this inspection.[/QUOTE]

I don't understand how the no-fouler deal will work. There's a certain amount of desired back-pressure between the cat and muffler/resonator so recessing the 02 sensor a half-inch further from exhaust gases won't buy you much.

I'll fess up and say I tried it myself a few years back on my daughters 2002 Suby Forester. The kluge job didn't work so I bought the cheapest Bosch sensor I could find and the little critter has not thrown a code in at least three years.

BTW ... I thinking in some areas ... if inspectors find owners have taken steps to defeat, or otherwise skew inspection results, there could be fines or vehicle impoundments.

The nice folks in your NC county wouldn't go that far would they? :whoa:

One last thought ... I believe any emission related code is retained in history for a minimum of 40 complete warm-up cycles. I suppose any / all inspection stations have a different rule book but you might want to see if your folks want a clean history.

snicknc 08-29-2010 07:01 PM

Re: P0421 Code
 
Well, did the non fouler mod. I also reconnected two vacuum lines that had become disconnected from the back of the intake.

Unfortunately, P0421 came back on, so I guess I'm down to changing out the pre-cat. Bank 1 is on the front of the engine, right? That's really all I can see it being at this point-- I'm not getting any more codes.

Chazberry 08-29-2010 08:39 PM

Re: P0421 Code
 
[QUOTE=snicknc;1654563]Unfortunately, P0421 came back on, so I guess I'm down to changing out the pre-cat.[/QUOTE]

I'm sorry you wasted your time, but I'm a little relieved - I'd hate to be responsible for getting you fined or having your vehicle impounded. ;)

[QUOTE=snicknc;1654563] Bank 1 is on the front of the engine, right? [/QUOTE]

I'm not positive, but I thought Bank 1 was closest to the firewall - better double check.

Chazberry 08-29-2010 08:56 PM

Re: P0421 Code
 
2 Attachment(s)
Found some stuff in the files (Bank 2 is up front) . . .

snicknc 08-29-2010 10:59 PM

Re: P0421 Code
 
Wow.

So it seems it could still be an O2 sensor then. I'd actually looked up the positions previously, and it seemed to indicate that Bank 1 was on the front of the engine. I can't believe I mixed that up.

Well, I suppose I'll go back to pulling O2 sensors then. I'll revert that modded one back to stock and see what we have on the back two sensors.

Thanks for the heads-up.

snicknc 08-30-2010 02:52 PM

Re: P0421 Code
 
I called a muffler shop for a quote on a new cat (versus just welding one on myself), as I'm running out of time with this car, and the guy there said that the catalytic converter company he sources from stated that P0421 is an indication of coolant hitting the cat 90% of the time.

He went so far as to recommend NOT replacing the cat until I figured out what's causing the code. I guess the idea is that the cat is not actually failing, but is simply having its efficiency hindered. I know absolutely zero about the inner workings of catalytic converters, so does this sound about right?

I am not relishing the thought of head gasket change, but I'm not blowing any smoke at all, overheating, or seeing my coolant levels drop, so I'm wondering if it's actually the intake manifold gasket leaking (if coolant contamination is the culprit at all). I'll go ahead and pull the intake over the next couple of days, I suppose, and see what I can find. I just finished swapping the head gaskets on my brother's Dakota-- geez. Talk about the month of vehicle maintenance.

snicknc 08-30-2010 03:00 PM

Re: P0421 Code
 
I found this thread in the forum: 151713 (sorry can't post URL's yet, I guess)

which seems to point to 1) thermostat or 2) MAF. My temperature gauge is at 1/4 as opposed to the 3/8 - 1/2 range specified as "normal" in that thread.

As far as I know, neither has been replaced, but as I'll be pulling the intake anyway to do a compression check, I guess I'll go ahead and swap out the thermostat.

Chazberry 08-30-2010 03:28 PM

Re: P0421 Code
 
[QUOTE=snicknc;1654874]I found this thread in the forum: 151713 (sorry can't post URL's yet, I guess)[/QUOTE]

Dontcha hate it when threads end "unresolved"!
[url]http://www.saturnfans.com/forums/showthread.php?t=151713[/url]

[QUOTE=snicknc;1654874]As far as I know, neither has been replaced, but as I'll be pulling the intake anyway to do a compression check, I guess I'll go ahead and swap out the thermostat.[/QUOTE]

Be careful with the T'stat extension pipe - some folks have had the attachment tab break off. Do a search for tips on that job.

Sounds plausible about coolant affecting the cat, but strange that you're not losing coolant - maybe it only takes a tiny bit (?). Typically on this engine, people get coolant in the oil due to a leak in the Coolant/Oil Heat Exchanger - which you will see when you get the intake off.

Chazberry 08-30-2010 03:35 PM

Re: P0421 Code
 
[QUOTE=snicknc;1654867]...so I'm wondering if it's actually the intake manifold gasket leaking (if coolant contamination is the culprit at all). [/QUOTE]

Btw - I don't remember any intake gaskets separating coolant from anything.

snicknc 08-30-2010 03:55 PM

Re: P0421 Code
 
That's good info to know about the intake gasket. Given that it's such a minor leak, I think it's likely not the head gaskets. I've never seen them go in a small way, but I guess it's always possible.

Chazberry 08-30-2010 04:11 PM

Re: P0421 Code
 
[QUOTE=snicknc;1654892]That's good info to know about the intake gasket. Given that it's such a minor leak, I think it's likely not the head gaskets. I've never seen them go in a small way, but I guess it's always possible.[/QUOTE]

Yeah - this bizarro engine has a lower manifold that sits between the heads -
[url]http://www.saturnfans.com/forums/attachment.php?attachmentid=16667&d=1254936197[/url]
- and the Intake sits on top of that (no coolant passages in there).

I'm thinking the head gasket is the only way coolant could get into the exhaust.

snicknc 08-31-2010 10:02 PM

Re: P0421 Code
 
Well...

There is a hose that connects to below the throttle body and goes to the top of the coolant reservoir.

Looks like I have a few problems:

- Oil in the throttle body (probably PCV)
- A lot of oil in the intake (probably PCV)
- I broke a couple of clips off of those cheap plastic covers covering the solenoids? on the vehicle-left side of the intake. I'd read the disassembly instructions incorrectly and thought I had to remove the covers-- it's been a long week
- Doesn't look like I have spacer gaskets-- there's definitely sealant there, but no actual gaskets. I'm not a fan of lazy-boy gaskets like that, especially when the real deal is readily available. About par for the course, as according to the MX records, the dealership was the last one in there.

That muffler guy told me that oil slings P0420 (or maybe P0430-- I don't remember), but that it's coolant that slings P0421. Either way, I don't see any coolant leaks thus far, but my reservoir is a little low-- about 1/2 inch below the cold full line.

I'll pull the plugs and replace the thermostat tomorrow and keep looking.

Meanwhile, I need another post or two to be able to link, so I'll make a couple of bogus posts so I can link to a web album of what I've found so far. If you get a chance, could you tell me what you think?

snicknc 08-31-2010 10:21 PM

Re: P0421 Code
 
I guess I can't type ..., minimum of 5 characters


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