P0420 code and what I discovered

acamato · Jul 2, 2017

My van has been throwing a P0420 code for a couple of months. Lately it has had poor acceleration. I decided to pull the inline (3rd cat). This is what I found.

This inside of the cat is OK. It was plugged with the insides of the upstream cats. I assume the rear bank cat.
I am going to install a new third cat. I will leave the rear bank cat and install a spark plug spacer. If I keep on throwing a P0420 code I will replace the cat.

Can't wait to have a van with power again.

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MrRangerZr1 · Jul 2, 2017

Holy smokes! Pretty sure its from the bank 2 cat! Which van do you have, how many miles, and does the van have VCM?

I pulled my cats off at 120k miles and I did not find any loose debris, I only saw few small pebble sized catalyst pieces, probably a quarter size amount of it.

acamato · Jul 2, 2017

MrRangerZr1 said:
Holy smokes! Pretty sure its from the bank 2 cat! Which van do you have, how many miles, and does the van have VCM?

I pulled my cats off at 120k miles and I did not find any loose debris, I only saw few small pebble sized catalyst pieces, probably a quarter size amount of it.

I think it's from bank 2. That's the only cat that has been throwing a code.

It's a 2008 EX-L (Nav Res) with 102K. Yes to VCM. I recently installed the VCMuzzler II.

I could barely see daylight through the cat.

I got the new rear cat installed and it like driving a new van again. It's nice to have power restored.

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John Clark · Jul 2, 2017

I would HIGHLY recommend replacing all four O2 sensors in this case. Something killed that cat, especially at such low miles and if you just put a new cat in the same place you may cook that one as well. On these vehicles Honda used a wideband air fuel ratio sensor in the upstream sensor locations. Historically, the downstream sensors are just for checking for catalyst efficiency. However, when A/F sensors are used the downstream sensors also contribute to fuel trims so they do much more than just catalytic converter checking.

I would, at a minimum, replace the O2 sensors on the bank 1 side. Since it's always best to replace both upstream or both downstreams in pairs that means replacing all four would be the most prudent thing to do in your case. Best price for them is at RockAuto for the OEM NTK sensors. There's also a 5% discount code in the sponsor section of the forum here that can help with the cost. I'd just hate to see you replace that cat again down the road due to problematical sensors.

acamato · Jul 2, 2017

acamato said:
I think it's from bank 2. That's the only cat that has been throwing a code.

It's a 2008 EX-L (Nav Res) with 102K. Yes to VCM. I recently installed the VCMuzzler II.

I could barely see daylight through the cat.

I got the new rear cat installed and it like driving a new van again. It's nice to have power restored.

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The rear cat internals were ok. It was plugged with the internals from the bank 2 cat. I did not install a new bank 2 cat. I installed a new rear cat because it was plugged so bad that I could barely see sunlight through it.
I have to figure out what killed the bank 2 cat.

I am only $266 in so far (cat, shield, gaskets, nuts, bolts) and $60 is a core charge.

I am pretty sure my O2 sensors are ok. Just to check, I am going to log the O2 sensor data from bank 1 and 2 and take a look at it. I am using a Bluetooth ODBII reader and the Torque app to log the data.

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John Clark · Jul 2, 2017

Ok, I get that. I'm still confused, though. P0420 is a bank 1 cat code (rear bank.) You said the internals came out of bank 2 cat, which if bad would trigger a P0430. Bank 1 is the rear bank and bank 2 is the front bank. Did the internals come out of the rear bank cat?

As far as checking the O2's you can do that. However, the fronts are A/F ratio sensors and do not "switch" like you are used to on standard O2 sensors. It's much more difficult to troubleshoot them. I found worn out O2's on mine when there were no codes and they appeared to be functioning correctly on the scan tool.

Take a read through my experience with them here:

http://www.odyclub.com/forums/9-pro...025-honda-odyssey-pilot-accord-p0171-p0174-lean-conditions-high-fuel-trims.html

MrRangerZr1 · Jul 2, 2017

^Yep. P0420 is the bank 1 code. Which code did you have OP?

acamato · Jul 2, 2017

I had P0420. Never had P0430. I was posting from memory and mixed up bank 2 because of the 2 on P0430.

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John Clark · Jul 2, 2017

Usually what destroys cats is too much fuel or oil. Any history on the vehicle? How long have you owned it? Any previous repairs or issues? Overheats? Coolant burning can cause damage to O2 sensors which can, in turn, damage the cats if they're not working correctly.

acamato · Jul 3, 2017

John Clark said:
Usually what destroys cats is too much fuel or oil. Any history on the vehicle? How long have you owned it? Any previous repairs or issues? Overheats? Coolant burning can cause damage to O2 sensors which can, in turn, damage the cats if they're not working correctly.

I have owned the van since new. No issues prior to the cat issues except the battery crapped out on the NJ Turnpike. When the battery light came on, I tried to make it to the next exit. As the voltage in the van dropped other warning lights came on then the van died and I coasted off to the shoulder.

No overheats, no Engine issues. I recently did the timing belt.

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John Clark · Jul 3, 2017

Well, cats don't burn up and fall to peices like that for no reason. If it were me it would get new O2's all the way around. You may also have issues with one cat being hollow and the other one not. It's possible you have some damage to the other one too, causing it to be plugged, which would make that scenario even worse and pretty hard on the engine mechanically. If you're wanting to keep this van long term I'd get the cat replaced, check the other cat, replace if necessary, and then replace all four O2's. At a bare minimum replace the bad cat and both sensors on that side.

You can check that other cat by looking at the B2S2 voltage on a scan tool and looking for a fairly steady voltage there.

P0420 code and what I discovered

acamato

MrRangerZr1

acamato

John Clark

acamato

John Clark

MrRangerZr1

acamato

John Clark

acamato

John Clark

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