Question: Most likely situation with a PO4030 check engine code-

[Bluemill]

I've got a check engine for the first time in 10 years and 100,000 miles! Not a bad run huh? What great cars we have.
I have six speed, almost a daily driver, < 9000 miles a year, and I'm not Paul from Conn., C4-C5 Specialist, but I do take pretty good care of the car. My car is bone stock except for some light peripherals, like a Z06 air cleaner cover and titanium exhaust, smooth throat to the throttle body, and cut outs for cooler air in nose inner plastic.

I have never replaced an o2 sensor in all that time. So now it's throwing a PO4030, insufficient cat action on bank two. I've ordered some NTK downstream sensors, and hope that will do the trick. I would not like to buy a new cat assembly-whoa!!

Is it fairly easy to get at the sensors, or do you really have to drop the center set of pipes? I'm not finding any U-Tubes on this one.

Best,

Bluemill

 

[Toms007]

If you can get it up in the air, the O2 sensors are right there, easy to get to.

 

[Bluemill]

Thanks for the info and I'll get back...

That's good news, because those pipes have been on the car for 14 years, and even if they are stainless, (are they by the way?) I have to believe they would not be easy to remove.

I will advise the CAC of the results of replacing the downstream sensors.

Best,

Bluemill

 

[LLC5]

I've got a check engine for the first time in 10 years and 100,000 miles! Not a bad run huh? What great cars we have.
I have six speed, almost a daily driver, < 9000 miles a year, and I'm not Paul from Conn., C4-C5 Specialist, but I do take pretty good care of the car. My car is bone stock except for some light peripherals, like a Z06 air cleaner cover and titanium exhaust, smooth throat to the throttle body, and cut outs for cooler air in nose inner plastic.

I have never replaced an o2 sensor in all that time. So now it's throwing a PO4030, insufficient cat action on bank two. I've ordered some NTK downstream sensors, and hope that will do the trick. I would not like to buy a new cat assembly-whoa!!

Is it fairly easy to get at the sensors, or do you really have to drop the center set of pipes? I'm not finding any U-Tubes on this one.

Best,

Bluemill

P04030 is insufficient cat action as you stated, and that means the O2 sensors are working properly or you would not get that code. The cat is working, but not up to OBD2 standards. You will most likely need a new catalytic converter. Make sure that you are not losing any coolant, as coolant is a big contributor to cat failure. Good luck with it.

 

[Bluemill]

I tried the sensor on Bank 2- right side......

Thanks LLC5 for your response. Our family has had 5 Hondas BTW, going back to a '79 Accord. My Vette saver in the winter is a '07 Ridgeline- a popular family vehicle- " Hey Dad can I borrow the truck?"

I only had time to put in 1 sensor yesterday, right side, and I cranked it up and the MIL was still glowing. I'll put in the other sensor today, try resetting the code, and check it out after good long drive- an hour or so? Most did say the sensors were a longshot, but, it can't hurt if the originals are 14 yrs. old.

I will also look into the coolant level. I did do the orange 50/50 mix twice in the 10 years I've had the car, and I never remember any overheating issues. How about a vacuum issue? I've heard that is also a possibility. Is there a way to track that down? -other symptoms?

If I do need a center cat pipe I'll check with Dino's or reach out on the WTB pages. Brand new at $2700 just does not make sense!

Best always,

Bluemill

 

[Antz81]

. Brand new at $2700 just does not make sense!

The cost is partly due to the cost of the precious metals used for the catalyst.
even your old converter that's not functioning correctly will have value as scrap.

 

[LLC5]

Thanks LLC5 for your response. Our family has had 5 Hondas BTW, going back to a '79 Accord. My Vette saver in the winter is a '07 Ridgeline- a popular family vehicle- " Hey Dad can I borrow the truck?"

I only had time to put in 1 sensor yesterday, right side, and I cranked it up and the MIL was still glowing. I'll put in the other sensor today, try resetting the code, and check it out after good long drive- an hour or so? Most did say the sensors were a longshot, but, it can't hurt if the originals are 14 yrs. old.

I will also look into the coolant level. I did do the orange 50/50 mix twice in the 10 years I've had the car, and I never remember any overheating issues. How about a vacuum issue? I've heard that is also a possibility. Is there a way to track that down? -other symptoms?

If I do need a center cat pipe I'll check with Dino's or reach out on the WTB pages. Brand new at $2700 just does not make sense!

Best always,

Bluemill

If there was a false air issue (vacuum) you should be setting a lean mixture primary 02 sensor code bank 1 or2, etc. $2700.00 is a lot of money, but keep in mind that a lot of new aftermarket cat's set inefficiency codes, so if you do go aftermarket get a written free replacement warranty if you can. Good luck with it.

 

[Bluemill]

So close and yet so far.....

So over the weekend I put in both Downstream o2 sensors- pretty easy actually. Do be sure to have some temperature on the pipes, over 120 degrees they say, for it helps to prevent tearing out threads.

The immediate reaction was no MIL light, and the car was running so smoooth, like after a real tune up in the old days- 1970's or so when cars had contact points. I only did the downstream, after the cats sensors. I drove it twice on short trips yesterday, and kind let it be as it was the 10th anniversary of taking delivery of the car. i sort of wanted to "pretend" all was OK.

Drive it to work this am for the real test, 35 minutes, and about 17 miles in Boston rush hour traffic. No MIL booting the car real good....
Up to about 85 in third gear passing a naughty truck, and no light. I'm almost to the office, sitting at a traffic light, 31 minutes into the drive and 16 miles out and I start to do the fist pump........... and BAM, the little bugger lights up.

I have changed my GM orange coolant twice in 10 years, and it's right up to the line where it was 3 years ago when I changed it last, so coolant contamination does not appear to be a reason for failure.

So Corvette Buddies, do you know a C5 racer who took off his/her stock mid pipe assembly and put on an X pipe for more power at the track- who might want to clean up their garage?? Willing to pay FMV & shipping.

Best always,

Bluemill

 

[Bluemill]

PO430 is the code you don't want to get....and Magna Flow # 51397..............

This is a tough one to be sure of, and the expense of a cat assembly that doesn't fix it would really be a disaster. I am not getting any nibbles on the WTB pages for a stock H pipe.

Has anybody tried the "Y" pipe with cats from Magna Flow? I'd like to hear about someone who got one, and did it solve the PO430 code. So far I've only got one review and it said the light did not go away- but perhaps this owner had a more serious issue that was not corrected that continues to kill the catalyst.

I can't believe there is no one out there who can talk to this. Very little info on it.

Getting the free replacement guaranty is a biggy! That will be a must. The Magna Flow assembly is number 51397. I's stainless, it's almost direct fit, and it will sound like a MagnaFlow, not an Impala.

Best always,
Bluemill

 

[Bluemill]

PO430 is the code you don't want to get....and Magna Flow # 51397..............

This is a tough one to be sure of, and the expense of a cat assembly that doesn't fix it would really be a disaster. I am not getting any nibbles on the WTB pages for a stock H pipe.

Has anybody tried the "Y" pipe with cats from Magna Flow? I'd like to hear about someone who got one, and did it solve the PO430 code? So far I've only got one review and it said the light did not go away- but perhaps this owner had a more serious issue that was not corrected that continues to kill the catalyst.

I can't believe there is no one out there who can talk to this. Very little info on it.

Getting the free replacement guaranty is a biggy! That will be a must. The Magna Flow assembly is number 51397. I's stainless, it's almost direct fit, and it will sound like a MagnaFlow, not an Impala.

Best always,
Bluemill

 

[Bluemill]

No Codes TODAY!

So today I ran the car at higher revs than usual. Fuel economy was not the mission, keeping the MIL out was.

Last night the car only went about 6.5 miles and 12 minutes before coding. This was in almost city driving conditions. It seemed to getting worse and worse- setting the code sooner and sooner.

I have always been a slow revs driver to save on gas with the car. That's 10 years and about 86,000 miles of that type of treatment. I've only used 93 or higher octane fuel, and I would not lug the valves under any circumstances. I'm thinking carbon build up may be an issue.

Prior to startup this a.m., I reset the code on my OBD II. I went all 16.9 miles and 35 minutes without a code. Pretty cool.
I have heard from "the OTHER forum" that high speed runs tend not to set the code rapidly, while city driving does. I know this not a fix - YET!

Any body try a 51397 Magna Flow Y pipe cat assembly??

Also, is there an additive to flush out a converter- SeaFoam? STP, Chevron, or the like? It is not rattling, it does not smell, it's a freaking mystery!!!

I'd hate to buy a new converter and have it code again.

Best Always,

Bluemill

 

[Dad]

New cats?

Interesting, GMs pricing is a bit high since Rockauto has a set for about $440. Walker even offers them by the half without the "H" pipe.

 

[Hib Halverson]

Ok...I'm confused.

The OP says the code in question was a P04030.
Of course, there is no such five digit code.

DTCs only have a letter and four digits.

So, is the code in question an 0403, or is it an 0430?

 

[Bluemill]

Good catch Hib!................

Yeah, I screwed up. It's P0430. The code also is followed by the H and C. I'm at the point now where I concede I need a new cat, but I just hope that the old 02 sensors may have been the reason it failed. Soon I will have replaced both sets, at 101,600 miles, for the first time in 14 years and that many miles. All other symptoms are pretty clean. I add a quart of oil after about 3,000 miles, there is no coolant consumption, no exhaust smell- or smoke, the engine runs at about 196 F warmed up, and she really runs sweet! Could a bad VAF or air mass sensor cause a badly rich mixture to cook the cat?

Best,

Bluemill

 

[Bluemill]

The Kate Upton brutally hot tune up.......

..

Sorry Kate's not here, she busy calling her lawyer about the cloud thing releasing pictures of her....... My point though is I applied a lot of heat to the old cats today by letting it idle with the air on for 35 minutes in my driveway, then I drove it "Like I Stole It" for about another 40 minutes. It was a very hot day in New England today, 91 plus and humid, so the 35 minutes probably would have cooked whatever contaminant may have been ingested to the cats.

Paul, your fuel diagnosis may be right. The last full tank was from a Phillips 66 station that just changed ownership, and they dropped prices by like a dime on premium. That stuff is said to be top tier fuel, but not if it has been sitting for months because it was too pricey. Mmmmmmmm? I kind of had an inkling that may be the issue, and I put about 7 gallons of Shell and a jug of Techron when I had some space in the tank. One thing for sure, today I was likely burning a lot of that fuel after the heat up, for the entire time I was running it the revs were North of 2,000 rpm.

Too early to tell yet, but so far, no return of the MIL. That was for about an hour or so, and 4 key turns.

Tomorrow I'll put in the upstream o2 sensors, and for good measure put in some more premium- from a different, high turnover station.

Best always,

Bluemill

 

[Bluemill]

My PO430 engine code is fixed, don't buy a cat too quickly!


This time last week I was seriously shopping after market H catalytic converter pipe assemblies. Eight out of ten respondents thought the cat was fried on my car. The code said the right converter was not meeting OBD II standards.

Although I am still completely not sure it wasn't a fuel thing, for I had tried a different "top tier" fuel from a station that had just changed ownership. They also lowered price, like ten cents a gallon on premium, to make it a reasonable price for Top Tier. Who knows how long it was sitting around though- it may have been stale, or just not what C5's like.

Two weeks ago I replaced the downstream oxy sensors on a recommendation from this forum. The car ran much smoother with those installed, but it was still doing MIL's every 15-20 miles, and after, a half hour or so. No smells, no rattles, no coolant consumption- but 101,000 miles on the original o2 sensors. It looks like I should have done all 4 at the same time, for as soon as I did the pre-cat 2 sensors, the car has NOT thrown a light, and that's after 7 key turns, and 47 miles.

The same day, I also put in like 13 gallons of 93 octane at a high volume station, so the fuel may in fact have been the culprit, although I had put in 7 gallons of Shell and a bottle of Techron a week before.

So, don't go replacing your cats in a hurry if you throw a code PO430, check all the easy to do stuff first. Save yourself anywhere from $500-$3,000 if you avoid the H pipe replacement.

Best always,

Bluemill

 

[Bluemill]

The check engine light came back, shopping for Cats...

---

So after 157 miles, 6 days, and probably 20 key turns, the CE light kicked on again, and it is the dreaded PO430 again. I had replaced both sets of O2 sensors with NTK's, and put in 12.8 gallons of fresh 93 octane, and did a high temp cat cook, all to no avail.

After resetting, it only went 38 miles, and 3 key turns, before another MIL. Am I endangering the new O2 sensors with a failing cat?

After that many miles, time, and starts, I thought I had it fixed. I guess OBD II is accurate, and I should heed its readings. I only hope that the reason that the cat or cats failed was age and or old failing o2 sensors, otherwise I may replace the cat assembly at great cost, and then have it fail again. That would not be good.

My focus is the Magnaflo 51397, which is newer than the 31998, and looks to have smaller cats, and it's slightly more $.

Has anybody tried this one, and did you pass emissions OK?

Best,
Bluemill

 

[Hib Halverson]

Some facts about rear sensors and DTC P0430...

1) Rear sensors are for cat monitoring, nothing else so, changing them will not affect how the engine runs...no matter how much you think they may. To repeat...rear sensors do not affect engine performance as do front sensors.

2) The ECM uses the rear sensors to simply monitor cat performance in an indirect manner. Front sensor signals vary widely. If the cat is working properly, rear sensor signals will vary little. When the rear sensor signal starts to mimic the front sensor signal, the ECM assumes cat efficiency has dropped to an unacceptable point and turns on the MIL.

3) Whether or not you're using "top tier" fuel is usually irrelevant to a cat efficiency problem. The difference between a top tier fuel and others is the level and variety of detergent used in the gas. That can affect cleanliness of fuel system parts but will not affect "cleanliness" of exhaust system parts because the detergent is destroyed during combustion.

4) You can pour in "SeaFoam" until the cows some home but that will not affect cat efficiency in a positive manner. In fact, use of a lot of SeaFoam may negatively impact cats because SeaFoam contains a light oil and oil or oil residue in the exhaust damages cats.

5) P0430 is not usually a "sensor code". While it can set if the wiring to the rear sensors is faulty, it is almost always a "bad cat code".

6) Replace the cats

7) Be careful when shopping aftermarket cats. Some of the low cost products do not perform as well as stock cats.

 

[gmjunkie]

I agree with Hib!

PS It can sometimes take as long as 400 - 500 miles to set a emissions code depending What,and the severity of the problem!

 

[LLC5]

I agree with Hib!

PS It can sometimes take as long as 400 - 500 miles to set a emissions code depending What,and the severity of the problem!

And number of completed drive cycles.......