P0420 Cataclyst System Efficiency Below Threshold (Bank 1)
 

Im posting this to help others with the same "Check Engine" code

I bought the RX-8 used and it is a 2004 and lately I've been having this P0420 code going on and off every 2-3 days.

My impressions are that the car seemed slower lately but i really can't say for sure since im not very used to the car yet, other than that nothing seemed wrong...

*THE CAR IS STOCK*

1st trip to the dealer: they reprogrammed the car's computer and it went off. they gave the car back to me and the check engine reappeared on the same day later.. *WARRANTY is 5 years*

2nd trip to the dealer: they say they have to change the cataclyst but its under warranty so no worries. but in order to do that they also have to change the spark plugs and wires which aren't under warranty 292$CAD + taxes.
The car is staying at the dealer tonight and I'm supposed to get it back tomorrow!

At one point I was considering buying the COBB acces port (mazdamaniac) to mask the check engine code but I don't know if that was such a good idea on an ALL STOCK RX-8

So that's it for now! This could help out others with the same problem ;)

Have a nice day!

Simon

You do not need spark plugs and wires for the code you've mentioned. Your dealership was Bullshitting you, and you actually "believed" them.

Please try to understand how Emission system works before you spread any useless information.

This thread totally Failed.

they say the spark plugs and wires are bad. they say that it's what damaged the cat in the first place

is that better?

Sounds like another case of a dealership not knowing the fix, so lets try a bunch of things till we get it right, and then try to make the customer pay for as much stuff as we can.

A weak or failing ignition system could cause unburned gas to be swept through the combustion chamber into the catalytic converter, where it ignites and toasts the honeycomb.

So they can give him another cat, and he can toast that one too, or he/they can perform a little maintenance and defer the problem for a while, at least until the shitty coils burn out again and the process is repeated all over.

The plugs/wires could have caused the early demise of the cat... or if it was flooded enough to ruin the cat the plugs were probably shot anyway. I question the replacement of the plug wires without testing them first however.

new plugs and wires won't hurt, but could have done that yourself for half what they charged.

Okay, I pulled my codes today and this was one of them. Are we certain that it's a clogged CAT? I run a RP supercat with a Hymee exhaust. I also had to put in a resonator to reduce the noise levels. Any chance the glass pack resonator is causing the cell instead of the supercat?

The other code I got was P0139, 02 Sensor Circuit slow Response, Bank 1, Sensor 2. Is there a causal relationship between the two cells?

not necessarily clogged, but your cat is failing i.e. not converting the gases properly, time for a replacement

New CAT
 

So I was getting cels. The consensus seemed to point to clogged or failing CAT.
Looking at the "failing cat" as the new one is being welded in place, it appears almost good as new. I could see through the stainless steel baffles clearly.
IT clearly wasn't clogged. So what else would cause it to fail?

heat and too much unburnt fuel.

or it could be just sensor error.

I was thinking about the sensor...

I started getting the P0420 latetely

2005 GT MT

I seem to be burning gas quickly.

Im wondering if Im getting P0420 due to a bad O2 sensor, if its the case that would explain the fuel burning quicker.

Would have have a specific error about the O2 sensor ?

yes you could get code P0139, 02 Sensor Circuit slow Response, Bank 1, Sensor 2 as stated earlier in this thread. I am sure there are more for the o2 sensor but I am to lazy to look right now. Are you getting a blinking CEL by any chance?

yes those codes could result from bad sensor

bugster............

If its an 04 and you do not have the history..........

Plugs and wires are a good thing to do.

Im not getting a blinking CEL, just a solid one.

And the only code I got so far is the P0420.

I did a long trip (Montreal to Ottawa and back) today and gaz consumption seemed normal.

Maybe it was that 2h30 hour dead stop traffic commute in the snow storm 3 days ago, that skewed my perception of gaz consumption :)

I'll find a way to check the sensors and the cat.

Can a clogged cat cause P0420 ?

Dear RX enthusiasts please help!
About year ago my check engine light came on, diagnostic showed it to be P0420 "catalyst efficiency below threshold" and that was the only code I got. At that time I wasn't looking into that problem.
Couple of month ago I started to notice a lot of bad smell (burned gas) coming into the closed idling car, same thing on the traffic lights and whenever car was parked and idling, P0420 was constantly getting from the scanner.
So I started to look into that P0420 problem again and what I did is I brought my car to the mechanic, lifted it and unscrewed back oxygen censor, the one that located right into the catalytic. When I looked inside the catalytic - it was empty, completely. Mechanics checked that with the small LED light, they were able to stick it inside on its full length, about 15 inches. Both mechanics told me that their opinion is that insides of the catalyst converter got burned up and then blown out of the exhaust pipe, it took some time but now catalytic seems to be completely empty and clean out of debris.
I know that I still have warranty on my RX8, but going to a dealer (Giuffre Mazda)
was always too painfully - each time I felt extremely unwelcomed and not respected! But I guess I have no choice, hopefully they won't charge me for new cat.
My question is if anyone encountered anything similar to what I described?

Addition to previous comment:
'04 Rx-8, MT, 70K miles

Maybe I should check to see if I have anything left in my CAT...

It happened to me once, CAT completely burnt. you're at 70K so you are still covered.

Dont go Giuffre Mazda. They will try their best to give you some sort of bullshit, then make you pay (without fixing the root of the problem!)

Things like this you can go Manhattan Mazda, but expect it to take at least 2-3 days.

If you dont mind to drive all the way to jesery, you can try Wayne Mazda, they have the best service.

Thanks!
I made an appointment with Manhattan Mazda, hope they treat me better then Giuffre.
I'll keep you posted.

The service writer's name is hmm Kazy or something. a Big African American dude. He is pretty nice BUT he also refuses to cover most of the stuff thats supposed to be covered under warranty. Plus Manhattan Mazda's repair takes UNUSUALLY long (god an oil change takes 4 hours+) so what you should do is, drop ur car, take the rental and just leave.

Help!!!
Manhattan Mazda did find the bad catalytic, but now they saying that in order for them to do warranty repair on the cat, they have to change wires, coils and plugs, since they diagnosed engine misfire as well along with cat problem.
And I have absolutely no intentions to let them do coils, wires and plugs because of 2 reasons:
1) 2 weeks ago I changed plugs, and 2 coils (coils cost was 42$ at local Mazda parts) out of 4.
2) I have my mechanic who I trust and know for sure he can do same job for me at least twice chipper then Mazda.
I spoke with Mazda USA - they told me that dealer have their own procedure of diagnosing/fixing thing and I have to deal with that, they won't help...
So at this point my car is at the dealership, I can't take it without paying them diagnostic fee ( 250$), or let them do plugs/wires/coils for unreasonably high price + warranty repairs for cat. :(
Any advise???

tell them to replace the cat per warranty and if they attempt to make you pay for anything else to get the warranty work done that they will be in violation of state and federal law. tell them to put it in writing that you must pay for something in order to get the caT replaced under warranty so that you may provide a copy to the New York Attorney General along with your complaint and a copy to the court when you file the lawsuit

I did what you advised - got everything in righting, but don't think it will help me: As per Mazda's service guy, Todd:
ignition misfire caused catalytic converter to go bad and/or burn out, and according to their records - already happens second time (previous owner had it replaced in 6/06), so in order for mazda to do the warranty repair they need to make sure that it will never happens again and get read of the actual cause (engine misfire), which are replacing coils, plugs and wires. Also I spoke with the mechanics over there, and they told me that Mazda will not issue them new cat without getting all diagnostic results pulled from my car, so if 9 engine misfire (that's what they got) there, Mazda will not allow them to do Cat replacement, untill they clear the problem. Todd gave me full repair estimate - $1040 (that's with $250 diag. charge). Also I informed Todd about state and federal law, but it didn't make him more cooperative...
I figured it will be much chipper to get parts on my own and replace what they want at my mechanic shop and then bring the car second time for cat replacement...
So I paid $250 for what I already new, and got my car back.
This is where I am right now.
Any thoughts, gentlemen?