The Dreaded P0420 Code

[RH77]

The Teg threw a random code while driving today -- P0420 (unexpected oxy sensor readings, bad cat, etc.)

It hasn't popped back up, but I'm starting to worry if the cat is going bad. Not a cheap fix... 140K miles -- is this a reasonable amount of time (what's the average?) Could be a sensor...

Hopefully it was an EOC fluke (crosses fingers).

RH77

[Daox]

O2 sensors are easy to replace and a cat isn't too hard to replace either.

OBD-II Trouble Code: P0420 Catalyst System Efficiency Below Threshold (Bank 1)

[RH77]

That's a great site -- they cover some obscure codes that saved me in the past.

I couldn't consciously run it with a bad cat or sensors, so I'd have to fix it should it become a continuous problem. The goal of retaining the car is a combination of environmental and economical reasons, so those two factors sometimes don't agree.

Nevertheless, it would be a great time to replace the whole rattling exhaust system.

We'll see if the code returns...

-Rick

[SVOboy]

Hopefully it's just a fluke. Crazy computers

[Red]

I'm in the same boat with the Insight. Don't bother with any of the tricks on torching the rear O2 to see if its bad just replace it.

It is said that cats don't go bad, but just get caked up with sulfur. One trick I heard about but haven't tried yet is to pull the cat, dunk it in a lemon juice solution and bake it for a good 6-8hours

[taco]

i have had that code for years, no emissions testing = no cat

[Johnny Mullet]

If the exhaust rattles, the cat melted down and is throwing the code since it's not cleaning the exhaust like it's designed to. I removed my cat for performance reasons and simply tied my 02 sensor (downstream) to the frame and it keeps the light out.

[RH77]

Originally Posted by Johnny Mullet

If the exhaust rattles, the cat melted down and is throwing the code since it's not cleaning the exhaust like it's designed to. I removed my cat for performance reasons and simply tied my 02 sensor (downstream) to the frame and it keeps the light out.

The major rattle/buzz is coming from an inner-tube style A-pipe that busted loose years ago (very common Honda flaw). I pulled the heat shields as well -- all they did was rattle.

Something else further back is rattling -- likely the muffler. The 3rd random clanking occurs at low RPM idle -- the source can't be ID'd. It's a loud metal-to-metal clank/squeak.

I used a data logger to check the pre- and post-cat O2 sensors and compared the output to an expected voltage chart (about a year ago). It all was well, yet the rattles haven't changed.

What's the average service life on the converters? The car won't pass inspection without one (which is coming up -- plus I wouldn't feel comfortable with the emissions factor)...

-Rick

[Compaq888]

I've been told the cat life is about 100k. My exaust was making a weird noise and I went to the shop. They told me I had a crack in my manifold just from the test drive. They came back, took off the shield and showed me a huge crack with exaust coming out of my manifold. A new sound started a couple of months later and they narrowed it down to a heat shield. They told me just keep it there and don't worry about it.

[Formula413]

If you have an angle grinder and are pretty handy you can replace the cat yourself, most parts stores will have a direct fit replacement unit available. I changed one on my mom's Camry. Exhaust work basically involves grinding off some rusted bolts and slapping the new piece in. Usually.