code P0420. I had this same code 3 months ago and I ended up changing the 02 sensor. since then, I have not seen the code at all until today when I was cruising on the highway.

heres my other thread on the same problem
https://acurazine.com/forums/3g-tl-problems-fixes-114/check-engine-light-p0420-746712/

so if its been 3 months since the last code, and I changed the correct 02 sensor (assuming the old one was bad) what could it be now? do i have a bad cat? is that even possible after what happened the last time around?

 

it might be the 02 sensor for the other cat...

 

^but doesnt p0420 refer to bank 1 which is the rear secondary sensor? thats the sensor i changed the last time. p0430 is bank 2 which would be the other cat like your talking about

 

well when i had the P0420 i had to change the catalytic converter, Acura canada offers a waranty untill 130 000 Km so i got it replace it for free.

 

Take it to a smog shop and see if the convertor is functioning right or shoot it with a heat temp gun. The convertor should be hotter than the rest of the exhaust. Compare the two banks and see if one is significantly cooler than the other.

 

I forgot, emissions components are covered to 80,000 miles by federal law and I *think* but I'm not sure that it has recently been bumped higher. The convertor falls into this category and if you're good at talking, the 02s can be covered by it too.

 

p420 is the rear cat converter. bank 1 is always by the number one cylinder. you have to replace it. its covered under the factory emission extention of
7 years 70,000 miles or 8 year 80,000 miles depending on the state you live.

 

02 sensors or air fuel sensors are not coverd

 

Not supposed to be but it has been covered before. The argument was that the 02 sensors provide the feedback for short and long term fuel trim which directly effect emissions and convertor life. A bad 02 will cause an emissions failure. It has worked several times around here.

 

Either way they are both expensive so try to get it done for free.

Is this a Federal law or a Cali law that the cat is covered?

 

since i already replaced the O2 sensor on the rear cat, im going to assume that the cat is bad. i have 109k miles at this point so its not covered anymore. ill try the heat gun like IHC suggested and see what i get.

but since ill be installing the turbo kit as soon as it arrives, theres no need for me to replace the cat anyway.

 

I thought it was Federal but the Acura tech above probably knows better than me. I want to say 80K is Federal and the longer 100K may be state but don't quote me on that.

The only thing I can say for sure is that there is a Federal law stating an emissions warranty independent of the regular vehicle warranty.

 

ahhhh, yaa i would not worry about it.

 

Bypass the sensor.. You're going turbo soon, so you might as well.

 

the cel has not returned after a few days so i got a chance tonight to check the cats with my infrared heat gun after a long drive. the front cat (closest to the bumper) was reading between 400-500 degrees F on different parts. the rear cat (closest to the firewall) was reading between 500-650 degrees F on different parts.

Does that sound normal?

 

That's somewhat normal since the front cat has much more airflow over it. If you take the extreme of 250 degrees difference it's a lot but it sounds like on average they're not too far apart.

However I should've been a little more specific. The real tell-tale sign is the temp difference of the pre-cat and post-cat temps on the pipe right at the head and right after the cat. Compare those between one another. The temps going into the cats should be the same but the temps coming out will tell you if one is not functioning. If the exhaust is the same or cooler on the outlet, chances are the cat is not working.

 

I checked the temps again tonight after my drive home. the car was idling for about 15 minutes before i checked the temps so the cats had some time to cool down.

The front cat read 450ish degrees F right after the head and 320ish degrees F right after the cat. The rear cat read 500ish degrees F right after the head and 350ish degrees F right after the cat.

 

WAIT.

So is my local dealership telling me that my P0420 code is a result of my CAI? Are they just trying to be cheap and trying to avoid replacing my CAT? They replaced my o2 sensor and I'm still getting the code.

 

OK...this p0420 code is basically popping up almost every other day and I keep clearing it with my scanner. Like i said before, iver replaced the rear secondary sensor (bottom sensor) and the code didnt appear for a while but now its back all the time.

Does this code in anyway refer to the top o2 sensor on the rear cat or is the cat itself toast?

 

I don't know the answer to the code iteself. But I do know what the computer looks at in order to set the code. The top sensor is for feedback for the computer. The bottom sensor is only there to test the efficiency of the convertor. The computer compares the values of the top and bottom sensor and it's looking for them to be different from one another (cat is working). If they read the same a code will be set (cat not working). If the voltage is too low or too high it will set a code. There are other reasons to set a code but none that pertain to this.

Back to my point, it's possible but unlikely that the top sensor is off a little, making the top and bottom read too close to the same. Not likely though.

I'm surprised the outlets on the cats were cooler than the inlets. They may have cooled too much. If you have the chance to do it again, try it holding the rpms at 3,000 for a minute to make sure they're lit off.

Out of curiosity, does this code seem to set more often when you're driving easy? Has the car ever had a misfire issue?

I don't know your driving style and it's probably a bad convertor but sometimes driving the hell out of it will bring a cat or 02 back for a little while. At the minimum I would drive a little more aggressively. Even if you're not on it hard, hold each gear a little longer, keep rpms at 3,000 or above most of the time and see if the code comes back.

 

It only throws the code when im cruising and never at wot. It seems to always be happening in 5th gear when rpms are between 1500-2000. Prior to this week, the code would only show when it was at or below 55 degrees. The other day was the first time the code appeared when it was above 70.

I do mostly highway driving (60 miles a day). Im generally cruising but I do drive rather aggressively hitting 5k+ rpms a few times a day