P0420 (1 Viewer)

[goldigital]

Had P0420 for the last 2 weeks that showed up in super hot weather, ... mechanic strongly recommended replacing all Oxygen and fuel/air ratio sensors, there were actually 4 of these Bank 1 and Bank 2 (before and after cats)
Drove yesterday for about 10 minutes and P0420 showed up again! :-( ... damn!!!

Did anyone of you had to actually replace the catalic converter? which seems to be next step, just that it would be little bit out of the ordinary? ... would hot weather/temperature "kill" the catallic converter ???
I have no power loss, no problems at all drives like a dream! .. she has only 160K miles on

Scanned it and have this freeze frame for anyone that can chime in ... big thank you!!!

 

[crimsonaudio]

I ended up replacing my cats with aftermarket high-flow models then installed the URD rear 02 sensor simulators - zero issues since.

 

[goldigital]

I ended up replacing my cats with aftermarket high-flow models then installed the URD rear 02 sensor simulators - zero issues since.

I see, ... sorry what's URD rear 02 sensor simulators? thx!

 

[tone33]

I see, ... sorry what's URD rear 02 sensor simulators? thx!

I'm looking for this too... for off-road use only, of course. Don't see any threads on mud about it (or maybe my search skills need help).

 

[Jeremy9A]

Might not be legal where you are but....you can get an 18mm spark plug non fouler. Drill the center out with a 1/2" drill bit so your downstream sensor can thread into it. They are the same thread as your oxygen sensor.

It will space your sensor out of the exhaust stream and keep the code from returning.

 

[kidphc]

Your mechanic isn't very smart. Po420/p0430 always has been a catalytic inefficiency error message.

S1 on the manifold/before the cat measures Fuel air mixture, ECM adjust injector pulses for it. You usually a fast refresh rate, if you look at the sensor on the scanner in graphical mode you will see a large amount of fast up and down movements in the waveform.

S2 (post or center of the cat) should be a slow moving almost smooth looking waveform compared to S1. Goes up when you step on the accelerator and drops off when you let go, still should be smooth.

PO420/P0430 triggers when S2 (post cat or inside of the cat) has a pattern that mimics x% (x percentage, set by the manafacturer) of S1. Basically, the S2 sees is the gases are identical as S1 and the cat has not done its job. In graphical mode on the scanner they almost look like copies of each other.

Any mechanic that suggest anything other then replacing the cat should be smacked then taught what the ECM/PCM is looking for. The idiots on Youtube should just be shot, for miss information like using Seafoam will clear the code. No your scanner or the battery disconnect off camera cleared the code.

 

[atnolan94]

Your mechanic isn't very smart. Po420/p0430 always has been a catalytic inefficiency error message.

S1 on the manifold/before the cat measures Fuel air mixture, ECM adjust injector pulses for it. You usually a fast refresh rate, if you look at the sensor on the scanner in graphical mode you will see a large amount of fast up and down movements in the waveform.

S2 (post or center of the cat) should be a slow moving almost smooth looking waveform compared to S1. Goes up when you step on the accelerator and drops off when you let go, still should be smooth.

PO420/P0430 triggers when S2 (post cat or inside of the cat) has a pattern that mimics x% (x percentage, set by the manafacturer) of S1. Basically, the S2 sees is the gases are identical as S1 and the cat has not done its job. In graphical mode on the scanner they almost look like copies of each other.

Any mechanic that suggest anything other then replacing the cat should be smacked then taught what the ECM/PCM is looking for. The idiots on Youtube should just be shot, for miss information like using Seafoam will clear the code. No your scanner or the battery disconnect off camera cleared the code.

Wow man. There is a lot to unpack here, but first of all you could stand to be slightly more respectful.

It is not unusual on this platform to replace the downstream O2 sensors to cure this code. The catalytic efficiency is measured by...you guessed it...your downstream O2 sensors. A fault in the O2 sensor that does not result in a loss of voltage feedback will not always present with a code that says you have a bad O2 sensor. My 100 got a P0430 4 years ago, I replaced the appropriate downstream 02 sensor and cleared the code and it has yet to come back. An O2 sensor is $50, so why not try this before throwing $1000+ at it for new cats. In the case of OP, it sounds like the fact that O2 sensors did not fix it would indicate that he should look at the cats. There are examples of guys buying new cats and getting the code back and replacing the O2 sensors for it to never return. If it is an either/or scenario, why not try the cheaper option first? And is there really any harm in replacing O2 sensors? Not one bit.

You are just trying to prove a point, lighten up. Saying someone deserve to be shot is dramatic...we are talking about a CEL on a 15 year old car.

 

[jerryb]

I don't have cats, do you know why I see 420 on occasion? I certainly don't need knew cats.
Plenty of instances where cats ought to be the last thing a mechanic goes for.

 

[kidphc]

Wow man. There is a lot to unpack here, but first of all you could stand to be slightly more respectful.

It is not unusual on this platform to replace the downstream O2 sensors to cure this code. The catalytic efficiency is measured by...you guessed it...your downstream O2 sensors. A fault in the O2 sensor that does not result in a loss of voltage feedback will not always present with a code that says you have a bad O2 sensor. My 100 got a P0430 4 years ago, I replaced the appropriate downstream 02 sensor and cleared the code and it has yet to come back. An O2 sensor is $50, so why not try this before throwing $1000+ at it for new cats. In the case of OP, it sounds like the fact that O2 sensors did not fix it would indicate that he should look at the cats. There are examples of guys buying new cats and getting the code back and replacing the O2 sensors for it to never return. If it is an either/or scenario, why not try the cheaper option first? And is there really any harm in replacing O2 sensors? Not one bit.

You are just trying to prove a point, lighten up. Saying someone deserve to be shot is dramatic...we are talking about a CEL on a 15 year old car.

You are right I should be a bit more respectful.

If there are issues with O2 sensors such as switching rates, frequencies, voltages etc. They generally will throw a separate o2 related code. If you get an O2 code and the cat codes, you definitely want to diagnose the O2 first.

A simple test for if it is in fact the downstream O2 is to switch a know good one for the one in question. For a dual cat motor taking it from one bank to the other will often be enough to validate. If you can always look at the live stream data first on the good side, so you can get an idea of what you want to see. At least that way you don't have to spend money. Do it all the time with coils and miss fires. To validate it is the coil and not the cylinder (mechanical, injector, wiring/connector).

The cats on the LC are terribly expensive, talking aftermarket list prices DC and BRExhaust are 3-5k (wholesale 700-1600). These cats must be coated heavily in expensive metals. Makes sense why thieves drool when they see an LC. So changing them is not a trivial thing

We haven't changed many downstream O2 sensors, usually they only need replacement when the heater element fails internally. I guess they should wear out, just haven't figured a diagnostic routine to validate repair.

Most of the cats we pull are damaged from miss fires. They are usually empty or missing chunks or were garbage catalytic converters, like the early Nissan Armadas.

My LC has 277k and looks to have the original cats. So I am kinda curious to the internal condition of the OP's cat and his mileage.

 

[kidphc]

I don't have cats, do you know why I see 420 on occasion? I certainly don't need knew cats.
Plenty of instances where cats ought to be the last thing a mechanic goes for.

Do you have simulators?

 

[jerryb]

a calibrator.
if frequency and gain aren't adjusted right I can see 420 and 30. It's pretty finicky.
I was kind of being an ass. Probably shouldn't have. But honestly all sorts of things could be wrong on the vvti LX/LC and get a 420-30. Clearly, zero feedback or even missing narrow bands get you the same code.

 

[kidphc]

I was kind of being an ass. Probably shouldn't have. But honestly all sorts of things could be wrong on the vvti LX/LC and get a 420-30. Clearly, zero feedback or even missing narrow bands get you the same code.

True, many things can cause all different codes. Hence why it is important to do a diagnostic. Even an exhaust leak can throw a PO420-430 code. Personally, never saw one that we have done one in the shop that was an O2 or exhaust leak.

Best for me was a Grand Prix, threw P0446 (evap leak), he had taken it to another shop, replaced a ton of crap. I spent 6 hours running the usual test, everything checked out. Charged a partial diagnostic told him to go to the dealer, but come back and tell me what it was. Fricking dealer goes oh yeah, $600 its the ABS computer. They replaced the module, encoded it did all the usual. Customer said he was shocked that it could be it, but the code didn't come back in 6 months, the time it took to visit me again.

 

[jerryb]

wow, and dealers aren't s*** lol. oops.

if the vvti headers leak back up through the secondary air tubes you'll get 420-30 also in the vvti's.
that's the only provable leak I've seen.
I've seen water, condensation on a cold humid morning leaking out both ends of cat pipes and not trigger any codes.

 

[kidphc]

wow, and dealers aren't s*** lol. oops.

if the vvti headers leak back up through the secondary air tubes you'll get 420-30 also in the vvti's.
that's the only provable leak I've seen.
I've seen water, condensation on a cold humid morning leaking out both ends of cat pipes and not trigger any codes.

I consider the dealers specialist. All they work on are particular makes and models for the most part. So they are more likely tosee more issues with those models.
As a general repair shop. I am working on a Honda one minute, changing the oil on a Merc 5 minutes later and changing the brakes on a Dodge next.

Alldata, in my personal opinion has gone to a bit of s***. Half the TSBs are listed etc.

Thanks for the information on the VVTI motors. We rarely work on (only one customer) LC/LX so my knowledge on them is low. It is slowly increasing because of MUD and having to work on my own truck.

 

[HBovrlndr]

Might not be legal where you are but....you can get an 18mm spark plug non fouler. Drill the center out with a 1/2" drill bit so your downstream sensor can thread into it. They are the same thread as your oxygen sensor.

It will space your sensor out of the exhaust stream and keep the code from returning.

I went this route and have not had the code pop back up.

 

[NoTempoLimit]

if the vvti headers leak back up through the secondary air tubes you'll get 420-30 also in the vvti's.
that's the only provable leak I've seen.

@jerryb Thanks for this info. I have a 2006 with VVTi. I started getting the codes after my fuel pump cut out climbing a long grade in the Mojave at 108ºF. Good thing it happened on the way OUT of California (one way trip). I replaced the post-cat O2's and that resolved the problem - for a few weeks. Then the codes came back along with the dreaded idiot light. ScanGage paid for itself every day.

Since the Federal Reserve, whatever their reasons may be, refuses to let me have any of this 0% interest money, I can't just throw costly parts at my truck.

I installed O2 spacers (bought on Amazon, not hard to find) and that resolved the problem. Not sure about the long term, but I have much more pressing maintenance issues to deal with. So this band-aid has to stay.

The cats on the LC are terribly expensive, talking aftermarket list prices DC and BRExhaust are 3-5k (wholesale 700-1600). These cats must be coated heavily in expensive metals. Makes sense why thieves drool when they see an LC. So changing them is not a trivial thing.

@kidphc The $3-5k price, is that for new OE cats? What do you mean by "wholesale 700-1600"?

 

[BullElk]

@kidphc The $3-5k price, is that for new OE cats? What do you mean by "wholesale 700-1600"?

Is replacing the cats just to get the lights to go off or are there other tangible reasons to get the 0420-0430 codes to not show up again? What are the ill effects to the LX of just leaving the CEL on rather than the costs of cats?

 

[jerryb]

I don't know that there are any. I never noticed any over a whole summer with pending and current 420-30 while I was messing around. As long as the screen says 300+ miles I didn't mind.
The fact that there are wideband sensors in the front is enough for me being that they pretty much control the trims anyway. But then the rears are so tight and finicky- designed by toyota- denso - that it's irritating.
The only thing I look at is the front voltage and the swings that it makes, and fuel trim- lately. Just to make sure they aren't dying.
I couldn't even say that it's always in closed loop with a current 430-20.

I wish I could alter the fuel maps, ignore the rear sensors and ignore the SAI. Wish me luck on the power ball.

 

[BullElk]

I don't know that there are any. I never noticed any over a whole summer with pending and current 420-30 while I was messing around. As long as the screen says 300+ miles I didn't mind.

I haven't noticed any either. My code has been on and off for several years now. I sho ain't replacing the cats just to turn the lights off. If I did, then I would be a LX owner whining about the high cost of ownership. I recently bought a very nice 2000 LX for less than just the cats.