forcemac

My 2005rl just started displaying the p0420 code. I read here that a lot folks try change out the post O2 sensor. I was wondering if there was anyone here with some photos showing how it was done or at least where it is located exactly? I am a novice car person, but not against to turning a wrench.....thanks

forcemac

Also, according to the manual there is a primary and a secondary
O2 sensor, both with front and rear (bank 2, bank 1). So i guess i need to know which is the most commonly replaced...primary rear or secondary rear?

Megatron

A P0420 code is telling you the rear bank catalytic converter is working below normal levels. The O2 sensors themselves being faulty will throw different codes. Of course, this is not to say a faulty O2 sensor can't be the reason your cat efficiency readings are low, but usually in that case, you throw multiple codes.

I would reset your CEL and see if the same code comes back. If it does, and it's only a P0420, I'm afraid it's more likely that your rear cat needs to be replaced. Just remember, a P0420 is the REAR Cat... the one hanging off of the rear cylinders between the firewall and your engine. Don't get confused and replace the wrong cat!

yungone501

iTrader: (4)

^^^correct/agreed

P0420 on an engine with 2 or more catalytic converters is generally for bank 1 catalyst which is the the side of the motor with cylinder number one which would be the catalytic converter on the back of the engine.

The code tha was pulled simply implies that the post catalyst oxygens sensor has detected that the catalyst has been recognized as not performing properly. This does NOT mean that the catalytic converter is bad. You could have a bad O2 sensor (post catalyst), faulty wiring between O2 sensor and ECM, bad ECM or of course a bad catalytic converter.

There's a few things that I would do before replacing any parts.
1.) Run an entire can of SeaFoam through gas tank at a high concentration. I generally run one can with a full tank of fuel. This will remove any contaminants (carbon, oil, burned fuel soot, etc...) that have been trapped or collected on the wafer design of the catalytic converter itself. This obviously would decrease or greatly affect the performance because the precious metals used to superheat exhaust gases are now covered and unable to be activated by not being in direct contact with the heat from the engine.

2. Take it to a REPUTABLE (and I do mean REPUTABLE) exhaust shop to have the catalytic converter tested. Try and call ahead of time to see if you could wait while this is perfromed. If they accept, try and be present for the test and see if the technician will show you the results as he's obtaining them. If they refuse to check the car while you wait, be skeptical and search for another shop if you don't feel assured by the words given over the phone. I say all of this because I'm in the automotive industry myself (electrical/drivability diagnostics and repair) and if there's one thing I've learned over the many years it's that exhaust shops are nearly as bad as transmission "rebuild" shops. Anyways, two tests will be performed. One to ensure the temperatures are being elevated and are being done within a certain range and next pressure drop test to determine if the catalytic converter is not plugged up. The first test is the most important test in your case because you want to ensure that the catalytic converter is doing what its supposed to be doing: superheating the exhaust.

Now the reason you want to literally see the results while they're being obtained is because it's not unlikely that any exhaust shop that you visit will say that the catalytic converter "tested bad" even if it didn't. This is why it's so important to find a reputable shop and read all the reviews that you can find. I'm not sure why everyone of them do this but unless you take these few steps, you will more than likely just be another victim.

IF in the event the SeaFoam did not work and the catalyst checked good, I recommend taking it to a shop that specializes in drivability/emissions related diagnostics and repairs. Find someone of some place with great reviews (all shops have a few bad reviews but the good ones have way more good) and take it to them. If in the event you are told to replace the catalytic converter, don't freak out because it tested good. It's still very possible. Don't skimp out and buy an aftermarket catalytic converter. Use only OEM Acura converters...wether you buy a new or used one make sure it's an OEM. Also, you're better off buying a used one over an aftermarket one.

yungone501

iTrader: (4)

Oh yeah...

You have a total of 4 oxygen sensors on the RL. There are two on each bank and there are of course two banks. On each bank, there's one O2 sensor before the catalytic converter (primary) and then one behind the converter (secondary). The primary O2 sensor on bank 1 is referred to as Bank 1 sensor 1 (or B1S1) and the the secondary on bank 1 is bank 1 sensor 2 (B1S2). This is also the same for bank 2.

So you have:
Bank 1- B1S2 and B1S2
Bank 2- B2S1 and B2S2
That totals 4 O2 sensors.

As I mentioned on my first post above, bank 1 is always on the side of the engine with number 1 cylinder on it. The other side of the engine is referred to as bank 2.

Megatron

yungone501 gave you some very good info above. However, the only thing I'm not sure about is whether you should go to different shops and have your Cat tested. If it's cheap to do... great! But if each place charges you an hour labor or more at $100+/hr and you have to go to a couple of places just to find out in the end it really is your cat, then you're already out a couple hundred bucks that you could have applied to your cat replacement to begin with.

I guess the one piece of info we all forgot to ask the OP is what is the mileage on the car??? If it's around 150K or more... it's more likely the cat. It it's less, it's possibily other things. Consider the mileage before you decide whether to just change the cat or go through some places to diagnose and test the cat.

yungone501

iTrader: (4)

Yeah sorry, I'm real skitzy about exhaust shops testing catalytic converters. And if you're only paying a few hundred for a catalytic converter, expect it not to resolve the P0420 code from reappearing and/or it failing within a years time. The reason why aftermarket catalytic converters (if that's what you're referring to) don't last as long as OEM is because they use less amounts of the precious metals that are what make up most of their cost. I've learned...hopefully you guys that are leaning towards the lower cost learn before you make a $200-400 mistake.

Megatron

Sorry I didn't mean to imply that the OP get an aftermarket cat. I'm definitely a believer in oem only! I'm just saying a new rear cat from online Acura dealers are just shy of $600. If the OP spends a few hundred testing the existing cat, just to find out he needs to replace the cat anyways, that's a few hundred toward the new cat he could have saved. That's all I'm saying. I think the mileage on the car will give a better indication of which way to go.

acura05rltl

ok guys i had same cade came in few days ago ...and i jast changed 02 snsor day..so far i drive 90 mil.and cel light did,t came back yet..

acura05rltl

hope fully that,s jst a 02 sensor ,,i will let u know

acura05rltl

120 mil driven since i changed the 02 sensor soo far soo good...also gatting good mpg than b4

oo7spy

Any time the car thinks it is having an issue with emissions it will change the way the engine runs to reduce emissions there. This will hurt MPGs and power.

forcemac

Well, i put the seafoam in and filled up from chevron, vice filling up on base (edwards, afb), and light went out after about 20 miles. Been off for two days bow, and i get abou 27mpg....seems to have done the trick. Btw, i have 108.5k miles on it....neighbor agreed with the progression of additive, different fuel source...then maybe the o2 sensor....

acura05rltl

hey guys ..i been gatting p0420 code 4 while ...so far i did some work by mysalf as much i know..(changed 02 sensor ).(put seafoam 2 bott)..but i m still gatting p0420 code..after 02 sensor car did runs like 120mil (little longer)and than code come back ...oem cat cost alot as u guys know....any one know somethink else to fix that issue...or do i have to change the cat...thanks

acura05rltl

i have 05 acura rl.176***mil

Megatron

At 176K miles, it wouldn't be out of the ordinary to really need a new cat, especially after having done seafoam and O2 sensor replacement.

acura05rltl

can i use tl-s type cat..or i have to have rl...becase tl-s cat cost little less...

oo7spy

IIRC, the RL, TL, and Accord 3.5L all use the same size/fitment cat. The only difference besides price has something to do with the ability to stop emissions, but all three are interchangeable. The Accord is the cheapest.

acura05rltl

007spy ...can u find me a accord part #...i m confuse ..i need bank one rear cat...and also what manifold..the cat is b4 manifold or after..or it,s one whole think.....

oo7spy

FYI, you can click on the little blue arrow next to the quoted user to go to that post/thread.

oo7spy

This also seems like it belongs here. Or we could merge.

waltthizzney

Are the Bank 1 and Bank 2 Cats interchangeable? If i was to buy a MagnaFlow Direct Fit Catalytic Converter are they the same part for either Bank 1 or 2?

thoiboi

https://www.oemacuraparts.com/v-2010...ust-manifold-2


Different part numbers so i'm going to say no..