P0420 AND P0430 At the same Time
 

2003 EX-L 3.0L V6 AT 155,000 miles

I bought this car a couple of weeks ago with existing light body damage and an existing brake issue. The car hadn't been driven in several months due to the brake issue, expired plates and a seemingly dead battery needing to be replaced. It would start but only with a jump.

After replacing the brake master cylinder and filling the battery's cells with water (all of them were extremely low) the car was now drivable and would start on it's own power. Not knowing how old the gas in the tank was, I siphoned out what I could and replaced it with fresh. I then ran half a bottle of Sea Foam through the vacuum line to clean out whatever it could. I also checked the plugs to see what kind of shape they were in. They looked pretty good. They are NGK Irridiums. I did adjust the gap to .033 because they were gapped at .040.

Due to it not being registered, I couldn't really drive it anywhere other than around my neighborhood a little bit which I did after fixing the brakes just to check things out. The car runs very well, it's quiet and the drive-train is very responsive.

I got a 3-day permit from the AZ DMV and took it in for emissions testing yesterday and was told it couldn't complete the test because it showed 2 systems not ready. Apparently, the car had not completed a drive cycle. I drove it around throughout the day running errands, etc. Late yesterday afternoon, I started it and now the CEL was on. I took it to Auto Zone and P0420 and P0430 presented.

In an effort to do my due diligence, I searched and researched this situation and could find no other threads here or on another forum where both these codes were present. I did, however, learn that in nearly all of the cases where one of the two codes were present, the cat ended up having to be replaced.

My questions:
Since both of these codes are being thrown, is it possible there is something wrong with the ECM/PCM or perhaps something else and that's why they are both present?

How do I determine which cats are affected since there are three?

Where should I start to troubleshoot this situation?

2 things are in play here that make this a very time critical situation:
1. Only 2 3-day permits can be issued for any vehicle in a 12 month period. The current one is the 2nd since I was issued one 2 weeks ago when I moved the car to my house from the seller's.
2. If I take the car in for testing and it can't complete for the same reason, the vehicle is then locked out of the system and must be inspected by a state sanctioned garage for compliance before it can undergo any further testing.

Any help and suggestions will be greatly appreciated.

I made this thread over in DIY about the readiness codes. But I had a 2003 4-cyl, so I never owned the shop-manual supplement for V-6. I'm guessing the general idea of the readiness codes is the same. Maybe you haven't satisfied all the specific things for some of them. It's not as simple as "how many drive cycles".
https://www.hondaaccordforum.com/for...s-codes-28313/

Hi Jim, thanks for the reply.

I should have been more specific. I looked up the necessary steps to successfully complete the cycle and get all systems in a state of readiness. I did that yesterday and upon completing the cycle, the CEL illuminated which brings me to my current situation.

thanks again,

Steve

Bumping up and hoping...

In the shop manual that I am looking at, the spark plug gap should be 0.039 - 0.043 in. Where did you get your spark plug gap? Those iridium plugs (NGK 1ZRF6K11) are gapped properly out of the box.

Google 'P0420 P0430 Accord V6'

For instance:

To be honest, I can't remember where I read that. I've done so much reading and research over the past few days that I can't remember where it was.
Using the info you posted, I re-gapped the plugs to .041 and an interesting thing happened.

The first couple of times I started the car, it stumbled and had to be started again. On the second start each time, it fired right up with no hesitation or sputtering and ran smoothly. The next time I started it, which was a couple hours later, I actually drove it that time. About 5 miles into that trip, the CEL went off and stayed off until the next time I started the car. Same thing happened again. At that point I was really scratching my head because, I mean, considering all the things that could throw those two codes, the spark plug gap is a pretty far stretch, isn't it?
The very next time I started the car, the light stayed off and hasn't come back on as of this post and I've driven the car probably 10 times since it went off and stayed off.
I stopped at Auto Zone before they closed tonight to get the codes read and there weren't even any stored in memory. Odd...?

Thanks everyone for the posts and suggestions. This one has me baffled but at least I'm pretty confident I can take it in for emissions on Monday and not have any issues.

Well - hoping for the best :)

Thanks for keeping us up to date on what is going on.

The gap is important to deliver the proper spark to the engine. Considering you had performance issue from both catalytic converters, I think the spark plug gap was the problem or definitely part of the problem.

When reading your last post, I can't tell if the check engine light never turns on now, turns on then turns off, or the check engine light just turns on for the bulb check.

Thanks for reporting back and hope that you resolved your issue.

It's visible when starting the car (key on, engine off) but does not remain lit once the car is started.
Thanks!