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Discussion Starter · #1 ·
Hello All,

I know there are other threads and my eyes are bloody from reading...

I just need some clarification:

1. My assumption is to replace both upstream and downstream sensors on bank 1 and 2 before replacing the cats, yes?

2. Bank 1 is on the back of the engine by the firewall?

3. Bank 2 is on the front of the engine by the radiator?

My emissions test is coming up in April and need to get ready for it.

Thanks.
 

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2008 Ridgeline RTS in Billet Silver Metallic
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Yep, I believe you have located them.

 

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Unless you put contaminated fuel in the vehicle, it is somewhat unlikely you have two defective catalytic converters or more than one defective sensor simultaneously. These two codes could also be a symptom of a different problem. If you feel like gambling, you can start throwing parts at it. In a case like this that doesn't have a clear cause, I'd be inclined to let a Honda dealer diagnose the problem using proper test procedures and the appropriate test equipment.
 

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2008 Ridgeline RTS in Billet Silver Metallic
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It has been my experience that everytime a P0420 code is thrown, the automatic dealer response is replace the cats. I'm getting the same response from my indie Honda guy too... and I'm telling him I want the O2 sensors replaced first.

I figure if nothing else, after 120k miles, they (the sensors) need to be replaced. My indie guy says he may have another trick up his sleeve. I'll see what he has to say. I plan to put the Pilot down for the TB service sometime this week and hopefully will find out about that trick soon.

I get the P0420 code every few months or so. It could be a while before I have any confidence that whatever is done to the system has fixed it.
 

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Hello All,

I know there are other threads and my eyes are bloody from reading...

I just need some clarification:

1. My assumption is to replace both upstream and downstream sensors on bank 1 and 2 before replacing the cats, yes?

2. Bank 1 is on the back of the engine by the firewall?

3. Bank 2 is on the front of the engine by the radiator?

My emissions test is coming up in April and need to get ready for it.

Thanks.

Before you do anything I would see a doctor about that bloody eye thing....
 

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It has been my experience that everytime a P0420 code is thrown, the automatic dealer response is replace the cats. I'm getting the same response from my indie Honda guy too... and I'm telling him I want the O2 sensors replaced first.

I figure if nothing else, after 120k miles, they (the sensors) need to be replaced. My indie guy says he may have another trick up his sleeve. I'll see what he has to say. I plan to put the Pilot down for the TB service sometime this week and hopefully will find out about that trick soon.

I get the P0420 code every few months or so. It could be a while before I have any confidence that whatever is done to the system has fixed it.
I got Cat replaced 2yrs ago at Thanksgiving time when code check engine light. Truck is nearing 150,000 miles now just got back from trip to Myrtle Beach SC last week. Have not seen check engine light since dealer replaced cat.
 

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Discussion Starter · #8 · (Edited)
Thanks guys.

Let me throw this at you. Last year, I only had the P0420 code on.
In Ohio we have a mobile emissions test truck that will sit by an highway ramp and monitor cars and trucks that pass by. I received a letter saying I was not required to have a test because my truck was in the top 5% of best emissions! This year is another story and will have to go in.

Why would I have a code but still test in the top 5%?

213,000 miles
 

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2006 Ridgeline RTS in Steel Blue
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Only a Guess,

They've have a number of "Failures" with 2006 RL's. Or It's 10yr's Old and they typically see issues arise about then?
 

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Discussion Starter · #10 ·
I guess...
The code says something is wrong and I can't pass the test because of the code. But, in actuality, it is perfectly fine????

I love this truck and am trying to keep it going as it drives like new.
 

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I could type pages of information on exactly how these sensors work, but here's a "kindergarten" version:

The pre-cat and post-cat sensors are different. The pre-cat sensors are more complex and are used to determine the actual air-to-fuel ratio. They are more important because they tell the computer if the engine is running rich or lean so it can make frequent, precise adjustments to ensure the engine is running at the desired air-to-fuel ratio. The post-cat sensors are simpler, old-school "oxygen" sensors that are used only to determine if the air-to-fuel ratio is changing in order to determine if the catalytic converters are doing their job. Pre-cat sensors respond quickly. Post-cat sensors respond slowly. The engine computer makes small changes to the air-to-fuel ratio and measures the time it takes for the post-cat sensors to react. The codes you're getting will appear if the response time is different than what the computer expects indicating a problem with the sensor and/or cats. This does not necessarily mean the vehicle is exceeding emissions standards, only that it could be. Vehicles don't have multi-gas analyzers and thus can't detect actual emissions, so they have to guess if allowable emissions could be above allowable amounts based on other parameters.
 

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My wife got a new vehicle and I got her 2007 ridgeline which I have always liked.
I noticed the engine light and error code PO420
My wife said it comes on and off for the last 2 years. It seems to come on if the weather is rainy and goes off when it gets hot and dry. I noticed many have this problem with less than 100k. It's had all other maintenance needed since new and has 253k miles and runs excellent. Every 100k they have changed belts, water pump, plugs, etc. I love my Ridgeline.
 

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2008 Ridgeline RTS in Billet Silver Metallic
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A lot of shops will tell you to replace the cat(s). Some here think replacing the O2 sensors will fix it.

I have a similar issue with my 2006 Pilot and an erratic P0420 code that I haven't resolved yet.
 

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A lot of shops will tell you to replace the cat(s). Some here think replacing the O2 sensors will fix it.

I have a similar issue with my 2006 Pilot and an erratic P0420 code that I haven't resolved yet.
After the light went out this last time, I filled the tank up with unleaded no ethanol gas to see if that keeps the light from coming on again.
 

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I had this code pop up on me several weeks back. Cleared the code and it hasn't came back on since. When I had it read there were like 6 different things it could possibly be. Figured if it wasn't just a glitch it will be back.
 

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Getting po0420 code since 2009 off and on.. I have never figured out why. When it was a company car the independant shop i took it to jokes that honda must have a timer..
Bought meter to check o2 sensors seemed to work fast and ok. I suspect there is a series of off on ignition starts with no errors before it shuts off. If it was me and emissions test i would reset light if on and get tested to pass...not any less immoral than vw lol.
 

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I've had similar experience as others with p0420. I tried replacing all the o2 sensors and that seemed to work for a while then the code came back. Finally after about a yr of it coming on and going off I just swapped out the cats to the RV6 High flows and have not had a the code come back since. Cat change seemed to be the fix for me.
 

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Getting po0420 code since 2009 off and on.. I have never figured out why. When it was a company car the independant shop i took it to jokes that honda must have a timer..
Bought meter to check o2 sensors seemed to work fast and ok. I suspect there is a series of off on ignition starts with no errors before it shuts off. If it was me and emissions test i would reset light if on and get tested to pass...not any less immoral than vw lol.
Keep in mind clearing those codes will also reset the OBD II readiness monitors. The vehicle won't pass an emissions test until each test completes and passes, so you'd have to drive long enough to complete the monitors and hope the codes doesn't reappear before the emissions test. :)
 
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