P0420 Acura Code - Catalyst System Efficiency Below Threshold

I have both
P0430 and P0420 on

What model and year is your Acura? you probably have to replaced both side catalytic converters.

05 mdx

I have a 04 with a po420

The catalytic converter is the most common cause that will trigger the P0420 code. You could try using high octane gas and fuel additives (some people claim that may fix the problem), but more than likely you have to replace the catalytic converter to fix the problem.

i have a 03 Acura rsx type s , with engine code p0420
if i want to replace the o2 sensor like you suggest ,which o2 sensor should i replace ?

You could start by replacing the rear O2 sensor.

i have a 03 acura rsx with the code p0420. i replaced my upstream o2 sensor and went to orielly's auto store and got the codes cleared. went to the emission test and failed due to not ready code from the catalytic converter and o2 sensor. the tech told me to do a 7 trip cycle for 2 days. on my second day the CEL came back on and I'm confused on what to do now. I have 10 more days til my tabs expired.

The problem was more than likely the catalytic converter and not the O2 sensor. It's a very common problem with all make and models.

I have a 1999 Acura tl and the cel is on I have replaced the cat both o2 censors the erg value and cleaned the ports and have had the light cleared in between every part change and that Damn light is still on my car is still acting up as well

Did you use factory catalytic converters and sensors? Usually replacing the cats takes care of the problem and is some cases you have to replace the O2 sensors as well.

I have a 07 TL type-s giving me the code p0420 and another code for my app sensor my car went into limp mode so I changed the app sensor still didn't fix the problem so I ordered the catalytic converter In the description it stated for firewall side. I was wanted to make sure this was the correct part for that code.

Yes that is the correct part

Hi Jenn! I have a 07 MDX, I was wondering if changing that fixed the problem?

Im having the same issue! cant pass smog due to Cat "not ready". cleared the codes and all, been +500miles since, still Cat is not ready. Went to honda and shows P0139 & P0420. I dont have alot of money to replace O2 sensors & Cat on a hunch, but also running out of options. can i replace both sensors and re-test, or gotta do all ?

have both P0139 & P0420, cant pass smog bec of the catalyst is "not ready". my tags are already due, i dont really believe the "drive cycle" solution as there isnt a definite method out there. I drive 70mi/day for work, so after 2 weeks of clearing the codes, it should be fixed by now. looks like i have to replace the O2 sensors + Catalytic converter -- so MY QUESTION: can i replace one of them: O2 front , O2 back, Catalytic , one by one to see what fixes it so i dont spend too much $$$ on guessing?

Yes you can. You could even try clearing the code first and using high octane gas for a few weeks, sometimes that could help.

had my codes cleared 3 weeks ago, had driven +500mi since then :(
So today, stopped by my mechanic, suggested we replace the rear sensor & cat the same time , so did my buddy that's works at Honda service dealer. This is only to get the Catalyst on a ready state to pass smog :(. Thanks for the quick reply.

And been using 91octane (I'm in CA.)

I have the p0420 just the only code i have i want to know which cat converter should i replace it said belowed threshold bank 1 i want to know is it the one that goes on the manifold or the one that after that

What model and year is your Acura?

06 tl base

Which one do i have to replace

P0420 is for the Catalytic Converter Bank 1. The Bank 1 on your Acura TL is on bank of the engine.

Ok thank you

Have 2008 TL base 170k miles. Engine light been on awhile has thrown the p0420 code several times looked at. Mostly only use high octane gas. Need emissions tested. Replace cat conv really only way? About how much should I expect to cost to fix? I have replaced the fuel cap, though fuel cap does still seem to be little loose. Occassionally when I can get a good seal on cap after getting gas, light does go off for a day or so. Thoughts? Thank you.

As far as I know the replacing the Catalytic Converter is the only way. The price depends where you live and the brand you use, but should range between $150-$500 for the part plus about 2 hours of labor. Some states requires higher standards than other.

I have an Acura Integra 00, and my check engine light is on. I bought a scanner to check what happened and came with the code p0420. I replaced catalytic converter and both o2 sensor, and I reset the car computer and drive 25 miles. The check engine light came up again. Can you help me in that please.

Did you got the same code? did you used a factory catalytic converter?

Before I changed it, yes. No I bought the cat from ebay

Unfortunately you have to check is there is the same code. Could be something totally different. Some of the cats sold on eBay are not very reliable. We have replaced some at our shop and weeks later we get the same code.

what is your best advice????

Start by checking what code do you have now, could be a different code.

I have an 2002 aruca TL base type.. my catalytic converter went bad so I'm trying to get buy a new one but first I have to find the emission code that's located somewhere under the hood. Can you guys help?

Unfortunately we can't look from here, but you just have to open the hood and look for a sticker similar to this one:

Hi I have 03 Acura MDX and I have that code P0420 bank 1 so I try to buy it to replace but I'm not sure which one I should buy they told me there two of them can please help me thanks!!!! Also I have the VTM-4 light comes on ... you think has something to do with the 02 sensor thanks again

For the P0420 code, the catalytic converter you need is the Bank 1 also know as "Rear Bank"

I have an 2007 Acura MDX, and recently received a code that shows P0420 Catalyst System Efficiency Below Threshold. Do you have any suggestions on how this should be fixed?

The problem is more than likely the Three Way Catalytic Converter. Replacing the Catalytic Converter usually takes care of the problem. Before you replacing the Catalytic, you could try using high octane gas for a couple of weeks and if possible ad a fuel additive. If the Catalytic Converter is not deteriorated, high octane gas and fuel additive may fix the problem.

The vehicle has 3 Catalytic Converters. Any idea on which one would give this code?

Since you have the P0420 code, then you have to replace the Rear Warm-Up Three Way Catalytic Converter Bank 1

I have the code PO 420 and PO 304.. I need help!!!! Last time PO 304 came on and it was fix and now both of them is on?

My car is 2006 Acura TSX

What they did to fix the P0304 code problem? You should try to repair the P0304 code first before trying to fix the P00420 code.
The P0304 could be an spark plug, igntion coil or fuel injector; if one of those components fail, then it could also trigger the P0420 code, which is usually the catalytic converter.

How much will this cost to fix?

Depends on what exactly the problem is. What model and year is your Acura?

2007 Acura RL.

The most common problem that could set the P0420 code on your vehicle is the Catalytic Convert. A new Catalytic Converter from the factory could cost you around $2000, and aftermarket (non-factory) around half of that.

I have codes p0303 and P0420 on my 2012 3.7TL. I've changed all plugs and coils but I'm still getting that misfire code for cylinder 3, next I'm thinking of changing the injectors. Should I look into changing my O2 sensor also?

No, if you have already replaced the the plug and coil, then the fuel injector is the most likely cause and that could set the P0420 as well.

Can anybody help me get part # for the catalytic converter bank 1 for 2007 MDX? My mechanic told me it needs to be replaced. He told me the OBD code P0420.

Part numbers change all the time. You can find parts here: https://www.rockauto.com/en...

I have a 2002 rsx base model a/t. It says dtc not ready and then after I completed the readiness drive the P0420 below efficiency threshold bank 1 popped up. Thinkin about changeing 02 sensors or is it the catalytic converter? It has 178k miles on it also...

It would be best if you inspect the O2 sensors signal to determine the problem, but based on a national database of repairs for your model and year, the most likely cause of the problem is the catalytic converter.

Hi, I have a 2013 Acura TL Base Model. I got the P0420 code Catalyst System Efficiency Below Threshold Bank 1. Which part am I replacing? My car has 175,150 miles on it and I have seen my MPG go down. I'm getting about 19mpg when I used to get about 23.

The Catalytic Converter, which is the part that triggers the P0420 code, is not directly related to fuel consumption. However, if that is a problem with another component, for example a faulty fuel injector or Mass Air Flow (MAF) sensor, it will cause a low MPG and it can damage the Catalytic Converter.

At this point, I recommend not just replacing the Catalytic Converter, but having a mechanic check your vehicle for other problems. If possible, change the spark plugs and air filter, as part of the regular maintenance.