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P0430 With New Cats

I'm really thinking it's a bad cat at this point. The catalyst monitor hasn't run yet, but I can watch the O2 sensors and fuel trim real time. I can view the calculated cat efficiency, too, but only after the cat monitor runs. So I'll have to wait on that.

Here's my rationale:
- I didn't have a 0430 before the new cats (I had a 0420, which is the other side)
- Swapping upstream sensors didn't move the problem to the other side
- After swapping the downstream sensors, I can see that the mV of the Bank2 sensor is still really high compared to that of the Bank1 sensor so the problem didn't move when I swapped the downstream sensors either
- Long term fuel trim is within 1% of each other for Bank1 and Bank2

So after all of the troubleshooting and moving sensors around, the downstream sensor on Bank2 is still showing rich enough to throw the cat efficiency code.
 
Well the cat monitor finally ran and the P0430 came back immediately. It was very close, but failed because of a .008 difference in calculated efficiency.

The manufacturer of the cats (Eastern Catalytic) want me to call their tech support with the upstream and downstream O2 sensor values real-time before they'll consider a warranty claim. So I guess I'll do that next.

 

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So I spoke to the technician at Eastern Catalytic. He said there are a few concerns that don't necessarily point to a bad cat (even though I never had an issue with Bank 2 in the past).

- Long term fuel trim on both banks is high, indicating to him that the PCM is compensating for a rich condition. Bank 1 was around -13 to -14% and Bank 2 was -17 to -18%
- Cross counts for the O2 sensor on bank 2 are low. It's consistently hanging out at a higher voltage, slowly dropping to a low voltage, and then back up. I swapped the sensors and the behavior is the same on bank 2 so I don't know what to make of it
- The downstream sensor on bank 2 is indicating a rich condition that the cat can't compensate for because of whatever is causing that bank to be rich

So not much more information. He said a tune up might help. The plugs are about a year old, but the oil needs changed and I have no idea the last time the air filter was changed.
 
Clean the MAF sensor and throttle body for good measure while you're at it. Look for vacuum leaks too. Even though the plugs are only 1 year old, you may consider inspecting & checking the gaps.

Does fuel pressure hold steady after turning the motor off when measured at the fuel rail? Curious about leaky injectors..

Definitely work on getting those fuel trims closer to 0
 
BainMan said:
Clean the MAF sensor and throttle body for good measure while you're at it. Look for vacuum leaks too. Even through the plugs are only 1 year old, you may consider inspecting & checking the gaps.

Does fuel pressure hold steady after turning the motor off when measured at the fuel rail? Curious about leaky injectors..

Definitely work on getting those fuel trims closer to 0
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I haven't checked the FP after I shut it off. I'll have to do that.

MAF is original and never been cleaned, so I'll do that too.

The guy also mentioned a TSB for coil pack grounds on the LC9. Says the break and can cause a weak spark. I never heard of it but it can't hurt to check that out too.
 
Check spark plug gap and shorten the gap and see what happens.
Long story short it saved me $1200
.
 
ckeene said:
Check spark plug gap and shorten the gap and see what happens.
Long story short it saved me $1200
.
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I'll do that, too. At least on 7 of the 8. The #8 plug is a total PITA to get at...or was it #7? I don't recall exactly but it was one of the back ones.
 
turbojimmy said:
I'll do that, too. At least on 7 of the 8. The #8 plug is a total PITA to get at...or was it #7? I don't recall exactly but it was one of the back ones.
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Do you have swivels and different sized extensions? It makes the job not so bad on that last plug. I forget the order but it's something like this... starting from the spark plug socket, then a 4" extension w/ wobbler head, swivel joint, then another extension of whatever size to your ratchet. It would drive me nuts knowing 1 plug was gapped differently than the rest, ha.
 
turbojimmy said:
So I spoke to the technician at Eastern Catalytic. He said there are a few concerns that don't necessarily point to a bad cat (even though I never had an issue with Bank 2 in the past).

- Long term fuel trim on both banks is high, indicating to him that the PCM is compensating for a rich condition. Bank 1 was around -13 to -14% and Bank 2 was -17 to -18%
- Cross counts for the O2 sensor on bank 2 are low. It's consistently hanging out at a higher voltage, slowly dropping to a low voltage, and then back up. I swapped the sensors and the behavior is the same on bank 2 so I don't know what to make of it
- The downstream sensor on bank 2 is indicating a rich condition that the cat can't compensate for because of whatever is causing that bank to be rich

So not much more information. He said a tune up might help. The plugs are about a year old, but the oil needs changed and I have no idea the last time the air filter was changed.
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If you want to know if the cat is bad or not, then do the test I outlined way back in post #5.  That is very similar to the test your PCM does before setting the P0430.  I suspect your cat is bad and the post cat O2 sensor will quickly follow the pre-cat O2 sensor.

But before replacing your cat converter, figure out why the PCM has to compensate so much for a rich condition, or you will likely ruin a new converter again (as I believe you already have).  This has nothing to do with spark plug gap, and probably isn't the fault of the new converter.  Make them run rich and converters can and will have a meltdown.  If they give you a free replacement converter, it will be a gesture of good will - but I suspect that first you will probably need to convince them that you have your problem fixed and you won't be coming back to them a third time.

Good luck
 
Just a thought.... Could it be a flex fuel screwup of some sort?  No experience with them.  If it thinks it needs richer mix because of it identifying E85, but really has straight E10 in it - wouldn't that throw off the fuel trims negative.  The biggest problem I have with all of this is that it does not set a P0171 or P0172 which has to do with the PCM being able to control fuel mix as it desires.  It seems that something has taken out the converter in rapid fashion.  If not rich fuel, then something else.  I have also heard that internal coolant leaks are death to converters.
 
2004Slickside said:
Just a thought.... Could it be a flex fuel screwup of some sort?  No experience with them.  If it thinks it needs richer mix because of it identifying E85, but really has straight E10 in it - wouldn't that throw off the fuel trims negative.  The biggest problem I have with all of this is that it does not set a P0171 or P0172 which has to do with the PCM being able to control fuel mix as it desires.  It seems that something has taken out the converter in rapid fashion.  If not rich fuel, then something else.  I have also heard that internal coolant leaks are death to converters.
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Yeah that's my thing too - no rich codes. I really think the cat was marginal out of the box. The P0430 came on after only 125 miles and I never had a P0430 or any other Bank2 issues in the past. There is an alcohol level monitor/switch in the datastream. I'll have to check that out. But I'm really hoping a MAF clean and tune up will solve it. It's very close to passing. If not, I'll just live with it. I got my 2-year emissions sticker and I doubt there's 2 years of life left in the truck. It's a matter of principle at this point.
 
turbojimmy said:
Yeah that's my thing too - no rich codes. I really think the cat was marginal out of the box. The P0430 came on after only 125 miles and I never had a P0430 or any other Bank2 issues in the past. There is an alcohol level monitor/switch in the datastream. I'll have to check that out. But I'm really hoping a MAF clean and tune up will solve it. It's very close to passing. If not, I'll just live with it. I got my 2-year emissions sticker and I doubt there's 2 years of life left in the truck. It's a matter of principle at this point.
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Yeah, I understand - something to bug you and make you wonder....

Hey here's another thought.  What about engine and computer and body grounds?  Didn't you say that you previously had trouble with grounds due to rust?  They're easy to check with a voltmeter and it's easy to add additional ground straps.  'Lectricity does funny things in complex systems, and these Avalanches have miles of wiring.

The MAF clean is a good thing to do for whacky fuel trims.  If you want I can give you a chart of what it should read at idle and full throttle for various engine sizes.  You might want to at least write down the reading at idle for comparison before/after cleaning to see if it changes anything.
 
Here it is.  Of course you don't need to test 100% throttle at 5000 rpm.  You can design your own test for any RPM.  I would suggest maybe 85% VE @ 3000 full throttle (these LS motors have good heads).  That could be done riding the brake while going down the road.

From chart:  5.5 liter@3000RPM@80%VE = 130 g/sec
then MAF reading would be proportionately less for 5.3 liter:  5.3 liter@3000 RPM@80%VE = 125 g/sec
and MAF reading would be proportionately more for 85%VE:  5.3 liter@3000 RPM@85%VE = 132 g/sec

Idle will be off (for the RPMs) because of much lower volumetric efficiency at high vacuum and also the PCV contribution to total flow.  (no PCV flow @ 100% throttle)

 

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I cleaned the MAF and replaced the air filter. LTFT for bank 1 is a little better at around 13%, bank 2 is still higher (but better) at around 15%. All 4 O2 sensors are acting as they should - good crosscounts; upstream and downstream sensors are reporting pretty much the same values on both sides.

The manufacturer isn't going to honor the warranty on the cats unless I can get the LTFT under 10%, so I guess I'm done. I'm still convinced their cat is no good but I don't have any "before" readings. As I mentioned a few times, I've never had an issue with the right bank (bank 2) the 11 years I've owned the truck. New cats and now I have a P0430. Also - there's no rich codes of any kind. Just cat efficiency.
 
turbojimmy said:
So I've had a P0420 for years. At first it was intermittent, but then became a solid code a couple of years ago. In NJ we have to go through emissions inspection every 2 years. The truck is quite literally falling apart from rust, but mechanically it's fine. Runs good, 4WD works, so I figured I'd invest in the exhaust fix. I got a new set of cats from Eastern Catalytic and a Gibson exhaust system (which is quite nice and inexpensive). I also got 4 new O2 sensors.

With the new exhaust and O2 sensors installed, I unhooked the battery to recalibrate the fueling and cleared the codes. One by one the OBD-II monitors cleared and I was ready for emissions inspection. It passed, so I got 2 more years out of it so long as the body holds up.

At 125 miles since the exhaust fix the CEL came back on. It's a P0430 - cat on bank 2. No other codes. I cleared it, but it comes right back as soon as the cat OBD-II monitor runs. So...how do I diagnose? Eastern Catalytic won't process a warranty claim without a "trained mechanic" diagnosis which we all know consists of plugging it in and seeing a P0430 code. I'm not paying for a diagnosis.

I have a scanner that shows me expected and actual cat efficiency. I don't know if that's enough evidence for them. Not sure if swapping the new O2 sensors to bank 1 would make sense just to see if I get a 420 instead (indicating an O2 sensor problem rather than the cat itself).

It sucks because I was really enjoying the way the truck runs with the new parts - particularly the ability to remote-start it which I haven't been able to do in years.
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Hey, I just purchased the Gibson exhaust but it did not have the flex fitting. Are you having any issues not having it?
 
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