Hello guys I’m new to this site and also own my first 08 tl. My friends recommended me to join this site to get the hell I need to fix my car. Recently got the P0420 code. I’m not a mechanic but I do some preventive maintenance on my car you know the easy stuff lol. I was told my O2 sensors were bad or it can be that my catalytic converter is clogged. How did you fix this problem? Also how many 02 sensors the tl actually has? And last if I needed to get a new catalytic converter what would you recommend? Thanks in advance.

 

Welcome to the forums.

Since this is a topic/technical issue which will require replies and discussion, and not an introduction, this thread has been moved from the New Member Introductions forum to the model specific forum for better response.

 

Welcome to the community!

These cars have 2 monitored catalytic converters which contain a total of 4 oxygen sensors. There is one sensor before the cat, and one sensor after the cat, on both front and rear banks. The code you are seeing is for "Rear Bank Catalyst System Efficiency Below Threshold (Bank 1)".

The bank 1 catalyst is the one on the back of the block facing the firewall. If the cat is clogged you should have more going on than just efficiency code alone. When cats begin to clog up you typically pickup a misfire or some form of a driveablity issue as well. Is this something you have also been experiencing? Does it break up higher in the RPMs? Depending on the state of the clogged or failing cat you may also notice a sulfur smell.

If you are looking for the cheapest start, doing the downstream sensor on the rear cat may prove to be beneficial. While that is not guaranteed to fix your issue (it could also be caused by other things such as a wiring issue, a bad injector, or an exhaust leak) it is a good place to start and a common problem. If the code persists after the downstream sensor is changed, an up stream sensor may not hurt although the little bit of info I have to go off doesn't scream that's the case (diag is tricky over the forums so it's all speculation). You can also peek into the catalytic converter from the bung where the primary oxygen sensor threads in to see what kind of condition the substrate is in. This will give you a pretty good indication as to if it has failed.

If you do all of the above and still receive the code it may be time for a new cat - or a set of cats as they are not far behind each other. If it comes down to this I would recommend RV6s High Flow Pre-Cat setup. When compared to OEM replacements they are cost effective, and they will allow you to free up some extra horsepower. While the factory J-Pipe and catback will then become a restriction if you are going to pull OEM parts out anyway it makes for a great time to upgrade! You can find them on our website HERE. I can also get you OEM style Magnaflows - or new cats straight from Acura. If you would like pricing on either of those feel free to send me a PM.

Hopefully that helps you out a bit!

 

Don't replace the O2 or the cat just yet.

Put a pressure gauge on the exhaust and snap the throttle. You should not have any back pressure. You can also look at your O2 sensors.

 

Hi thanks for the response. i haven't been driving the car since i got the code, the car is my daily so i didn't want to risk it. i didn't get any misfires, issues while driving or sulfur smell which i think is a good sign. i was going to change only the upstream sensor on bank 1 but since you and other people told me to also change the downstream sensor ill change both and go from there. i will also check for exhaust leaks and wiring issues this weekend. i will keep in mind your recommendation on the RV6's although i forgot to mention in my post i got a free tsudo j-pipe from previous owner which i will put on soon, Anything i need to know before i do so? can you please help me with the right part # for the O2's or where to order them? thank you for your time and all the info, i really appreciate it.

 

thanks, i don't have a pressure gauge but i can have one of my friends check this for me.

 

Those are both good signs for sure! If you decide to replace the oxygen sensors feel free to send me a PM with your VIN and I can get you pricing for replacements.

The Tsudo Jpipe will bolt up to the RV6 cats if that is your concern - everything was made to fit factory flanges! If the Jpipe has been previously installed you are going to need replacement gaskets as well to make sure you don't end up with any exhaust leaks after that install. Aside from that the install is straight forward and should not be too big of a task with some basic tools and a floor jack (and jackstands).

If you need gaskets for the Jpipe I can include those in the O2 sensor pricing.

 

I would first clear the code and see how long it takes to come back before changing o2 sensors. It won't do any harm driving the car with that code.

 

You can rule in/out the catalytic converter and downstream o2 sensor by watching the fuel trims with a scan tool that has live data. There's plenty of info that can be found on google about what to look for. If you don't have a scanner you can get bluetooth dongle for like $10 on amazon and install torque or obdfusion on your phone and it will do the same thing.

 

Jotardio, what ended up being the problem and solution? I have had my 07 TL Type-S since March and have been getting that same code. 120K miles. Just moved from SC to Phoenix in June and thought the car just needed to adjust to the hot dry air, but after multiple resets of the code and some cata-clean additive, it keeps coming back. My exhaust does smell really bad - not sure it is the sulfur smell, but probably close.

 

replace the cat, it's dead, Jim.

 

Strange observation about P0420.
It popped up from time to time and stopped suddenly and now it's back.
I analyzed the period. The P0420 stopped to appear around the time when exhaust started to be loud. It cracked on this part for vibration absorbtion (don't know the name in English). When it was fixed, the code came back.
It looks as if the smaller flow (no crack) in exhaust is the source of the code. What do you think about it?

 

clogged cat

 

Probably, I had the same happen in my truck. The cat split at the seam, I had it welded back, then it started throwing a p0420. Scanner showed the o2 sensors were functioning so I replaced the cat and it's been good since.

 

I don't have third cat - there is new muffler instead 🙂.
Maybe the mufflers on back are clogged.

 

Third cat wouldn't cause a p0420, since it's after the downstream o2 sensor, so one of the first two cats.

 

I know but how the cracked exhaust after the first 2 cats could result in p0420 stopped to pop up 🤔

 

If it's after the downstream o2 sensors, I'd think it'd be unrelated.

 

Oh boy, here i go again . I just replaced the CAT and two O2 sensors on my wife's Odyssey minivan (cost a pretty penny) . Sadly last week i started having the same P0420 error code on my ACURA TL 2006 with 99K miles. . Cleared the Code with a OBD Fusion , and it came back after 15 miles. Don't know if it has anything to do with it, but I just did my Oil/Filter Change and decided to give my engine bay a quick wash (on a cool engine) .... shortly after this .... P0420 appeared.

Short of CAT replacements, can someone point to a remedy to maybe "just" replacing an O2 Sensor?

Noticed someone posted something about CATACLEAN fuel additive, willing to give it a try (seems about $20) but I don't want to make things worse. Did anybody done such treatment and did it help? from the ODBFusion, it seems to be just below the Threshold, barely, hence the code. Not sure if me washing the engine bay could have caused this? .... also I don't drive the car too much, so I can see how this could make things a bit worse, My TL does not see any Highway driving (which i know is not helping with keeping the engine clean) .... just overall too many short trips. I am original owner ... so yeah 2006 and i just hit 99000 miles.

Thanks for any tips!