My CEL is on, and I had the codes pulled today. I've got 2 codes, P0420 and P0174.

It seems like these could be related, from reading the description, but P0420 is for bank 1, and P0174 is for bank 2. Could one effect the other?

P0420 says it is cat system efficiency below threshold, and could be
- A/F ratio
- Air leak near the H02S Bank 1
- Ignition system concern
- Faulty catalytic converter.

P0174 says it could be:
- Large vacuum leak
- Fuel system concern
- Ignition system concern
- MAF sensor faulty
- H02S/AF ratio sensor fault

Another fact, I'm not sure if it is related, is that my air intake tube has a split in it. This is the rubber-like tube between the engine and the box coming from the air intake.

Any thoughts on what could be the issue? Since they are on different banks, does that mean that they are unrelated, and I have 2 problems to solve?

Glen

 

Also, does anyone know of a good diagram showing the locations of the sensors relative to the 3 cats?

If I understand correctly, Bank 1 is the rear cat, and there is a sensor before and after that cat. Bank 2 is the front cat, and there is a sensor before and after that cat. Is that correct? That would say that an issue in bank 1 should not affect bank 2.

If the above is correct, am I also correct that the H02S is the one after the cat?

Glen

 

I don't know if thread bumping is a no-no, but it's been over a week, so I thought I'd see if anyone is able to provide guidance.

I'm not sure if my two codes are likely to be interrelated, or two separate issues. Just looking for where to start. I found multiple diagrams showing the sensors and locations, but they conflicted, so I am unsure what to trust.

I picked up an infrared temp gun, so I can see if the cats appear to be operating, as I found a few threads that suggested that.

Anyone?

 

I have a similar problem on my Odyssey but only getting code P0420. You may want to check out this article:
http://www.tegger.com/hondafaq/p0420/index.html

I think I need to replace the front rear cat on mine. Sounds like you have a bad rear cat maybe.