Honda CR-V Owners Club Forums banner
  • Hey everyone! Enter your ride HERE to be a part of December's Ride of the Month Challenge!
1 - 19 of 19 Posts

·
Registered
2006 CRV EX
Joined
·
147 Posts
Discussion Starter · #1 ·
Hello,

2005 CRV 230,000 miles. Runs perfectly.

P0420 code.

Found exhaust leak between cat and pipe behind and added a new gasket, no leak now.

Drove 40 miles and light back on.

Could this be the downstream (rear) oxygen sensor? It looks old. Or is it definitely the cat?

How do I tell if the car has a problem that is ruining the cat?

Thanks
 

·
Registered
Joined
·
2,517 Posts
Your at 230k. The Cat doesnt last forever. There is no easy diagnosis unless the engine is running badly.

Personally, I would try the O2 sensor first. At that mileage it is most likely it has simply gone bad. But unless you have access to a proper scan tool (none of the DIY code readers are going to give information needed) that's the best place to start.

Sent from my SM-N975U using Tapatalk
 

·
Registered
2006 CR-V LX
Joined
·
255 Posts
If the O2 sensors are original at 230K miles, then it's probably time to replace them. Just might fix the P0420. Replacing the rear O2 sensor on a different car I had resolved the problem. Also, check the function and flow of the cat by using an infrared laser thermometer and check the temp of the exhaust pipe right before and right after the cat. After cat temp should be much higher than before cat temp. If the after cat temp is nearly the same, then the cat is probably plugged up and/or non-functional. If you car is running rich or burning oil, that will either kill the cat or cause it to not function until it's cleaned.
 

·
Registered
Joined
·
2,517 Posts
Missing some details of that test just fyi. Firing up a cold engine and trying that wont yield anything useful.

Engine needs to be at operating temperature, O2/catalyst monitors cycled so they are in control instead of default cold start program from the computer.

Which means reset codes with code reader when engine is cold. Start engine and set code reader to I/M readiness/emissions monitors or whatever your particular one calls them. Then drive with the reader hooked up for a while (including highway if at all possible).

Once O2 and catalyst related monitors have switched status from what they said after you clear codes (again this is code reader specific so just make mental notes) then you can read cat temps. Check engine light may return at this point to but probably not until you complete a second drive cycle (may see the 420 code reappear in pending codes).

I am curious how many people here say "hook up to scanner" have ever actually used one. Not trying to be a jerk but giving bad info is kind of pointless and not helpful. Quit using google and leave it to the techs. Live data and freeze frame, forget what's the emoji for "facepalm".

Sent from my SM-N975U using Tapatalk
 

·
Registered
Joined
·
1,009 Posts
Missing some details of that test just fyi. Firing up a cold engine and trying that wont yield anything useful.

Engine needs to be at operating temperature, O2/catalyst monitors cycled so they are in control instead of default cold start program from the computer.

Which means reset codes with code reader when engine is cold. Start engine and set code reader to I/M readiness/emissions monitors or whatever your particular one calls them. Then drive with the reader hooked up for a while (including highway if at all possible).

Once O2 and catalyst related monitors have switched status from what they said after you clear codes (again this is code reader specific so just make mental notes) then you can read cat temps. Check engine light may return at this point to but probably not until you complete a second drive cycle (may see the 420 code reappear in pending codes).

I am curious how many people here say "hook up to scanner" have ever actually used one. Not trying to be a jerk but giving bad info is kind of pointless and not helpful. Quit using google and leave it to the techs. Live data and freeze frame, forget what's the emoji for "facepalm".

Sent from my SM-N975U using Tapatalk
So if you have a scanner to see how the 02 is behaving, who cares change it anyways as it might fix it??
Who is giving bad info here ??
 

·
Registered
2006 CR-V LX
Joined
·
255 Posts
Missing some details of that test just fyi. Firing up a cold engine and trying that wont yield anything useful. Engine needs to be at operating temperature

Not trying to be a jerk but giving bad info is kind of pointless and not helpful. Quit using google and leave it to the techs. Live data and freeze frame, forget what's the emoji for "facepalm".
Yes, I am aware that it must be a fully warmed up engine and I did mention that in another thread with a similar issue and just neglected to mention that here. I also did not suggest to Brad that the engine should be cold. My suggestion is not "bad info" even if it's incomplete because I forgot to mention something. I post lots of threads and can't perfectly mention every detail each and every time. If Brad would have responded, I would probably have mentioned to him that the vehicle must be fully warmed up.

You're "not trying to be a jerk"? OK, I believe you, but you are coming across that way, just so you know. There is a proper and helpful way to say things, then there is an arrogant way to say things. You're a tech? Cool, then act like a professional with the heart of a teacher instead of trying to draw flies with vinegar because you're so flippin' awesome and we are all just a bunch of idiots. This forum is for everyone, not just techs. We are here to help each other and bounce ideas off each other and share our experiences and whatever knowledge we have. I have repaired an issue similar to this, so suggested the thermometer test. I have helped MANY people on another forum and am well known there to be helpful and to save people money and not insult those with less skill than I have. I have very patiently and kindly guided those with less knowledge than I have. Why? Because I care about my fellow human beings and want to help them. Are you here just to be right and smart and show us how awesome you are?

Maybe you are a skilled technician, and perhaps the greatest diagnostician on the web, but you have something to learn in how to get on with other people.
 

·
Registered
2006 CRV EX
Joined
·
147 Posts
Discussion Starter · #8 ·
No codes on the car now in probably 300 miles. Was throwing it in 40 miles. I believe that the rear oxygen sensor fixed it. I also replaced the front one which is a longer story, and am not sorry that I did. The old one looked really old.

Longer story:
My wife has a 2002 CRV. I didn't check the part numbers and assumed that the front sensor was the same. She has the 4wd and I have 2wd. So at some point I think it was still throwing a code and I put her front sensor in my car, it still threw a code and I went and bought a new front sensor. Then no codes. I then figured out the front sensors are different and that maybe during all the removing/swapping, I may have never tested my car with just the new rear sensor. It's not worth going back to me since it was only just over a hundred dollars and the old one looked beat. I did save it tho so I can pop it back in some day if that ever comes.

Thanks for all the help! I still may get one of those laser thermometers and test my cat temps. What kind of ballpark temps would be normal?

Thanks for all the help! I now have a great second car, bought for only $1700, to run longer distances since my primary car is a Mitsu electric that only goes about 60 miles.
 

·
Registered
2006 CR-V LX
Joined
·
255 Posts
It should be much hotter after the cat if it is working properly. That's how I knew mine was messed up, because it was about the same. Here's a video:

 

·
Registered
2006 CR-V LX
Joined
·
255 Posts
Thanks, I watched the video. I still am wondering how much hotter it should be, about. Thanks
Umm......like 75 or 100 degrees hotter or even more. Something like that. So, if the incoming is at say...….350 degrees, then the outgoing exhaust might be 425 or 450. I wouldn't get caught up on an exact number, but just that it is much hotter coming out of the cat than it is going into the cat. I can't explain the physics of it, but the catalyst material, if working correctly, actually increases the temp of the exhaust. If the temp isn't increased, then it's not working.

You'll want the vehicle fully warmed up (maybe some highway driving would help). When I did the temp test (on a Mazda Tribute) I increased the RPMs a bit to increase flow. In my case, the temp at the rear of the cat was about the same as the front of the cat (it might even have been a bit lower? I can't remember). That's when I knew something was wrong with the cat. I removed it and found it was all plugged up. A cat can also be non-functional even if it is very clean on the inside. After 350K miles on my Toyota Corolla the cat just isn't working even though it's clean. It was burning extra fuel earlier in it's life due to lean conditions (intake) and I think that helped kill the cat. I put a spacer on the newer rear O2 sensor and the car still runs fine now 40K miles later, which is 390K miles.
 

·
Registered
2006 CRV EX
Joined
·
147 Posts
Discussion Starter · #12 ·
Umm......like 75 or 100 degrees hotter or even more. Something like that. So, if the incoming is at say...….350 degrees, then the outgoing exhaust might be 425 or 450. I wouldn't get caught up on an exact number, but just that it is much hotter coming out of the cat than it is going into the cat. I can't explain the physics of it, but the catalyst material, if working correctly, actually increases the temp of the exhaust. If the temp isn't increased, then it's not working.

You'll want the vehicle fully warmed up (maybe some highway driving would help). When I did the temp test (on a Mazda Tribute) I increased the RPMs a bit to increase flow. In my case, the temp at the rear of the cat was about the same as the front of the cat (it might even have been a bit lower? I can't remember). That's when I knew something was wrong with the cat. I removed it and found it was all plugged up. A cat can also be non-functional even if it is very clean on the inside. After 350K miles on my Toyota Corolla the cat just isn't working even though it's clean. It was burning extra fuel earlier in it's life due to lean conditions (intake) and I think that helped kill the cat. I put a spacer on the newer rear O2 sensor and the car still runs fine now 40K miles later, which is 390K miles.

Thank you!
 

·
Registered
2006 CR-V LX
Joined
·
255 Posts
So, hook up a scanner and see what kind of readings you're getting from both the O2 sensors. I'm sure there are lots of videos on YT about how to interpret the readings. In my case with a Toyota, replacing the rear O2 sensor fixed the P0420 for about two years.
 

·
Registered
2006 CRV EX
Joined
·
147 Posts
Discussion Starter · #19 ·
Yes all is well! And on Friday I'm having the car inspected and having them replace the front bolts and springs at the exhaust manifold because the old ones are all rusted and won't budge. Also replacing the gasket up there with a nice felpro one recommended by others somewhere in my reading.

Then I'm going to switch out the stock cat for a $100 amazon cat and run that most of the time to save wear on the stock cat.

Oh, and with the $100 cat installed I'm going to do a Marvel Mystery Oil cleanse of the car to see if my oil consumption can be lowered - since I read that someone else had very good results, but that it can damage the cat.

That's another thread I will start later, but related to this one in a way...
 
1 - 19 of 19 Posts
Top