Codes P0420 and P0430?

Hello, although you are at a high mileage, catalytic converters fail because of some other fault, especially since this is both banks setting Cat efficiency codes. The fuel pressure code is also relevant, so if you can go into the engine computer and retrieve and historic codes that were set it would help, I would also go into the Mode 6 data it may be a little tricky to find but many scan tools will display Mode 6 data and the IM readiness monitors that have passed their self-tests. Mode 6 will list all the systems related to emissions and the tests that have failed. The catalytic converters will definitely list Not Ok or Failed since there are codes set for the cats. You may also be able to see some other fuel system related data.

But the live engine data PIDs you want to look at are the Long Term and Short-Term Fuel Trims (LTFT & STFT) for Bank 1 and Bank 2. Catalytic converters fail due to either a rich mixture, or contaminations entering the exhaust such as oil, coolant, etc. You will most likely see the Fuel Trims at a high number, ie +/-10% or higher. Check at idle and at 2,500 RPMs. If you see a high positive number, (ie +10% to 15% or even higher) the engine is running lean and adding additional fuel to compensate for what the engine computer determines to be a lean mixture so its adding fuel to the air/fuel mixture, which is not good for the Cats. If you see a high negative number (-10% to 15%) the engine computer is taking away fuel for an overly rich mixture. Either of these conditions can be Catalyst failing conditions, which is what needs to be diagnosed first. I agree with you about figuring out why the Cats are starting to fail, because if it's not diagnosed, the new ones may fail prematurely as well. This is why we need to know what fuel related code was set, even if it didn't come back yet. Some take time to come back, but it's very important.

The running condition can cause premature catalyst failure, cylinder misfires allow raw fuel (Hydrocarbons) or partially burned fuel (CO) down the exhaust. This prevents the Catalytic converter from being able to store oxygen. The converters need to be able to store oxygen so they can convert the emission gases into H20(water) and Carbon Dioxide (less harmful gases).
So, any cylinder misfires, or if the engine burns oil, goes through coolant, etc., need to be repaired first. There is a chance that if the underlying causes of the cat codes are repaired, they can burn off what's affecting them and start to function correctly again, but this is only if they are not too far gone already.
Under Mode 6 data you should also be able to see if any cylinders are indicating misfires, they will be listed as Ok or Not Ok.

Your fuel pressure is around 580.151psi at the time you recorded the data. Right now, if you were to monitor the rear Oxygen sensors, most likely you are going to see them fluctuate at a high frequency, 0.1v to 0.9v, this is an indication the cats are not able to burn off the gases it should be able to. This is a direct injection fuel system, so do not unbolt any of the high pressure steel fuel lines from the injectors, the pressure is so high you could be seriously injured, so go by scan data for now and let us know what the Fuel Trim numbers are at idle and 2500rpm. Also monitor the oxygen sensor data B1S2 and B2S2 (Bank1 sensor 2 and bank 2 sensor 2), these are your rear Oxygen sensors behind the cats in the exhaust. Make sure they are not stuck lean (low voltage, below 0.450v (450mv).

If the Fuel related code was something like a P0087 Fuel rail pressure too low, the ECM may increase fuel pressure to a higher level when it may not need to, this could be due to a faulty sensor or inaccurate data from a different sensor. This could cause a rich condition since these systems can reach 2000psi or higher in some cases. Check the engine oil and see if it is overfilled or smells like gas.
Many times, with these high-pressure systems, when there is a fault, the engine oil also ends up contaminated with gas and this only adds to the problem, causing the engine to run even richer. So, check the engine oil and go through some scan data and let us know what you see for Fuel trims.
I will post some further service information on those two codes, but we will see how rich the engine is running first and if you notice any other data PIDs that look out of place.
On your scan tool, try using the Global OBD2 generic side of the scan tool first when looking at Fuel trims, instead of the manufacturers side. Global OBD2 will give you more raw data, whereas the manufacturers side (Chevrolet in this case) might have substituted values in place when a fault is present. A bad vacuum leak will cause high positive fuel trim numbers at idle, and then they will go down at a higher RPM. Something to watch for.

Sorry for the long post, there's just a lot of information to consider with these codes. I suspect some high fuel trim numbers, whether they are positive or negative at idle and 2500 will give us some direction. Here's a few guides to read through as well. Let us know what you find, so hopefully we can address the issue quickly.

https://www.2carpros.com/articles/why-an-automotive-engine-will-run-rich

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Hello, I have written down some things that I thought may be of help on this issue. Hope its something that you can use. When I hooked my scan tool up to the vehicle and it started up the first thing I noticed was the J1850 VPW and the J1850 PWM both failed. Next, I went into the IM readiness screen and thought these may be of some help. Catalyst monitor- ok, heated catalyst monitor- n/a, oxygen sensor monitor- ok, and oxygen sensor heater monitor-ok.

I then went into the freeze frame data and made notes of the following items:
short term fuel trim bank 1- 0.8%
long term fuel trim bank 1- went as low as -5.5%
short term fuel trim bank 2- 0.8%
long term fuel trim bank 2- 4.7%
fuel rail pressure at idle- 11890 kPa
fuel/air commanded equivalence ratio- 1.047
long term sec. 02 sensor fuel trim- b1- 10.9%
long term sec. 202 sensor fuel rim- b2 - 7.8%
02 sensor test- all passed

Next I checked some of the on board monitoring :
limit type- min&max
Component ID- $04
Catalyst monitor B1 test value- 0.133
min limit- 0.187
max limit- 1.999
Status- Fail

Catalyst monitor B2
Component ID- $04
Test Value- 0.141
min limit- 0.187
max limit- 1.999
Status- Fail

All 6 cylinders misfires passed

Data Stream:
Fuel system 1 status- CL
Fuel syatem 2 status - CL
Calculated load value- 48.2%
Engine coolant temp- 81* C
Short term fuel trim bank 1- -5.5 to 4.7%
Long term fuel trim bank 1- -5.5%
Short term fuel trim bank 2- -7.0 to 6.3%
Long term fuel trim bank 2- -5.5%
Oxygen sensor output voltage-(b1-s1)- 0.760v
Oxygen sensor output voltage- (b1-s2)- 0.720v
Short term fuel trim (b1-s2)- 99.2%
Oxygen sensor output voltage (b2-s1)- 0.815v
Short term fuel trim (b2-s2)- 99.2%
Fuel Rail pressure at idle- 4200kPa
Catalyst Temp bank1 sensor1- 491*c
Catalyst Temp bank2 sensor1- 486*c
Long term Sec. 02 sensor fuel trim- b1- 10.9%
Long term Sec. 02 sensor fuel trim- b2- 7.0%

46 Times P codes have been set. Although some of them I went into showed to have no codes present. Here is the list of P codes I wrote down:
0014
0011
0089- fuel pressure regulator 1 performance
0300,01,02,03,04,05,06
0161
0141
0344
0137
2135
All of these codes were stored in the history. Only codes present were the 2 cat codes mentioned above in my first post.
I did forget to check the fuel trim numbers at 2,500 RPMs but I can get those if I need to for you.

Also, I just changed the oil a few days ago and when I checked it today it wasn't over filled, and the oil didn't smell like it was saturated with fuel. I hope all of this information helps you out with this issue. Thanks for all you've done already and sorry for my super long reply. I look forward to hearing from you soon.

I am also attaching a couple short videos i took of some of the data. Hope they can be of some use as well. Thanks again.

Okay, I'm copying all this data, as for the scan tool protocol type, I wouldn't worry about that too much, you were able to get onto the vehicles network and retrieve data, it looks like that's just the global OBD2 protocols and the scan tool searching for the correct one to communicate on. You could try updating the scan tool. There are constant updates for them. For the fuel trims, just pay attention to the data PIDs with Short Term/Long Term Fuel Trims, having the trims pulled up for each 02 sensor will just slow your scan tool down because its having to read more data, The less data PIDs you have up the faster the scan tool will refresh the live data.

When looking at fuel trims, just add the bank 1 LT and STerm together to get the total fuel trim for each bank, so looking at a frame of the trims you posted, Bank 1 +8.6(short term) and -5.5(long term) equals out to +3.1 total trim. Which is not bad, interesting both banks are stuck at -5.5 LT.
But if you were to graph that 02 data from the rear sensors you would see them fluctuating at a frequency that is too high for rear 02 sensors, that shows the cats are not storing oxygen which they need to be able to for burning off and converting the left over combustion gases.

What's the deal with all these codes? I know you said they were historic, but were they set prior to some repairs? Because that's a lot of concerning codes, misfire codes on every cylinder is not a good sign, I'm going to go through and look them up just to have a list. Along with the Cat temperatures in Fahrenheit (915f & 906f). If that data is correct, which I think those are estimated values, the reason why the Cat Eff codes are setting is because of the rear 02 voltage fluctuations. The voltage reading should be a much steadier, 600-700mv range or so, just not the high frequency you're seeing such as in the example waveform below.
If there were repairs done, and the cylinder misfires were taken care of, plus all the other code issues, this might be the aftermath and result of those previous cylinder misfires and possibly and over-fueling problem. I have heard of some people attempting to clean cats out or certain treatments, although I've never tried any, so I can't recommend something I haven't seen work myself.

The freezeframe data is from saved data from when specific codes set, so you would have to identify what code that data went with, one thing I see that's not good is the "fuel rail pressure at idle- 11890 kPa" - Thats 1724.49 psi at idle, I dent think that's within spec, and that is probably what set the fuel rail pressure sensor code.
I also see a P0137 B1S2 low voltage, more concerning is this 508-798psi @ idle for rail pressure, 1724.49psi would set a code.
The calculated cat temperatures look high to me as well, Id check them with a laser temperature indicator to see if they are actually that high, check the front and rear of each cat. Hopefully they are not already starting to melt down.

I've seen cats actually get so bad they melted plastic components on the engine. Glowing red when driving down the road, that's when they break apart and clog up the exhaust melting into a blob of rare metals,
To check if they have started to melt, you can do a back pressure test at either front oxygen sensor location, pull the sensor out and I use an adapter from an old 02 sensor hollowed out that has a hose on it, which I then hook my vacuum gauge too, the cheap kind that also go up to 10psi positive pressure. Hook it up and start the engine, you only need a quick reading at idle, then have someone rev it up once or twice while monitoring the gauge, if it goes over 1.5-2psi max, the cats are starting to melt down and restrict the exhaust. If they are reading 2psi at idle, it will jump up much higher with a quick rev, then you know the cats are done unfortunately. But that's the way to determine if they are beyond recovering. Don't leave the pressure gauge on the exhaust long, just a few seconds to get some readings.

Really it depends on the back story of this vehicle, with 42 codes set and some very apparent fueling faults in the past, it would explain the cats just having been so abused.
I'm going to look up these other codes.

I don't really have a history on the vehicle since I just purchased on the 4th of this month. It was hung up in park and the shifter wouldn't move but that was because the battery was so dead and wouldn't take a charge. it had been sitting for some time and all I have done to it is replace the battery and put gas in it.

Could you possibly show me your test sensor and vacuum gauge you are using to check the back pressure? I'm not fully understanding the hollowed-out part and the hose attached to it. I cleared the codes yesterday morning before I drove to work and usually when I start the car to drive home from work the check engine light has been coming back on, however when I drove home yesterday the light never reappeared. One thing I did forget to mention earlier is after washing the vehicle earlier last week and driving on Saturday I did notice on the rear liftgate what appeared to be some black soot that was kind of wet feeling and would just wipe off with my finger. Almost like it was something from the exhaust blowing up on the gate. Also, the exhaust tips are caked with black soot looking stuff. If I am reading your last reply correct it seems to me that the cats may be on their way out or are almost gone at this point.

Come to think of it, my daughter and I made a trip to town in it Saturday and when we arrived at our first stop it kind of smelled like rotten eggs according to her. Like I said, I just bought it and it's a really nice loaded vehicle that was destined for the scrap yard so I got a really good deal on it and if I need to replace the cats I have room to spend some money and still be into it for the cheap. Sorry for rambling on but I'm just brainstorming what I have noticed and letting you know about it. Thanks for your reply and I really appreciate the help.

Well your observations are great. If you're seeing soot around the exhaust pipe tips, it sounds like the exhaust is very rich, whether that is due to the cats not doing their job or the ECM is enriching the mixture because of inaccurate sensor data, or both is the question. It might be that the previous owner or shop was chasing some fault, and just started throwing parts at it, you might be able to tell what parts are new and they may have repaired the problem but by the time they were finished the cats may have been as well. It would explain all these codes and why you are only getting Cat eff codes now. They might be the only problem left, but the previous shop may have thought there was more wrong with it. It had been setting all cylinder misfire codes at some point, plus the list of codes which I've looked up each one. Some shops that don't want to test or don't know what tests to do will just throw parts at it until they fix it or give up.
As for the back pressure testing, you can get a back pressure testing kit which includes the fittings for screwing in a adapter into the front 02 sensor location. Here is a link to a back pressure testing kit, (2nd pic) is basically what I made myself, I took an old 02 sensor, broke off the sensor section and drilled out the threaded section, then attached a hose adapted so my vacuum gauge could attach to the hose. I just didn't buy the kit because I had every already. Due to the rubber hose though, you don't want to leave the gauge on there for long, I have seen someone melt the adapter and caused the melted tube section to actually fall into the exhaust through the 02-sensor hole, it was a really dumb thing for them to do. Anyway, besides that awful story, when you have the gauge hooked up, have someone sit in the vehicle so you can monitor the gauge, get a reading at idle, and then have them give it a couple little revs.
Surprisingly service info has back pressure testing instructions, first time I've seen that, but they want you to test both front Cats, one at a time. Now on some vehicles I have seen a 3rd cat, with no 02 sensor behind the 3rd cat, diagram 7,8 show the Three-way converter, so if both banks fail your front back pressure tests, if it happens that the rear (Post Catalyst) 02 sensor is after the front cats but before the 3rd cat, test at the rear 02 location and see if it fails the back pressure test at that location. For whatever reason some manufacturers don't always have an 02 sensor behind this 3rd cat, my vehicle actually has this setup.
If you fail your back pressure test at the rear 02 location, I would drop the front of the 3rd cat, and retest at the front 02 location again to see if the restricted exhaust is only effected by the 3rd cat, if it still fails at the front 02 with the 3rd cat front unbolted, then you know the issues are with the front cats. This will also give you a chance to visually inspect the 3rd cat's substrate from the front.

One thing I do before even going into all this type of testing is I remove the front 02s and take a look with my Bore Scope down the 02-sensor hole and see if the substrate looks like it's starting the melt down.

I've added a couple pictures 9,10,11 I took of a failing catalytic converter from a 4-cylinder Corolla. You can see around the edges where it had started to come apart, this was due to a failed Air/Fuel sensor heater circuit.
Pictures 12,13 are from a 07 Pathfinder that also had a failed cat, you can see the sections of the substrate that started showing signs of melting together. This was also from a failed A/F sensor as well; it was setting a code for the sensor, but it was already too late for the bank this cat was on. Sorry for the delay in posting, but I wanted to show these pictures as an example. With a very rich mixture the cat will start to overheat so much that it melts down into a ball of metal, blocking off the exhaust, and they can even break up into pieces and migrate down the exhaust into other sections, even getting into other cats or the muffler. You may or may not see this from the front view, but usually that's where the failure shows itself.
But in the testing method you can see that anything over 1.25 PSI is considered a failed back pressure test, most techs go with 1.5-2 PSI as a failed test. It would be nice if it's only the 3rd cat causing the issues, if it has one. Keep us updated and if you have any other questions.


https://www.amazon.com/Exhaust-Back-Pressure-Tester-Kit/dp/B0DHNF8MWW/ref=asc_df_B0DHNF8MWW?mcid=e7aef76852db3d34a3a6d90201733bf5&tag=hyprod-20&linkCode=df0&hvadid=712448966566&hvpos=&hvnetw=g&hvrand=2592928959495115489&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9009976&hvtargid=pla-2395504449241&psc=1