Hi fellow Fit owners, im a noobie Fit owner and a car novice in general. I apologize in advance if this very same issue has been covered, I'll apologize again if I'm called out on it

I have used the search function on this forum and google searches to learn about this code, but no thread or comment I have seen gave me a clear picture of what coarse of action to take next.

I will certainly appreciate any insight and help with the issue I'm having with this P0420 code that keeps showing up. My car is a 2007 Fit Automatic sport with 94,000 miles. Previous owner took good care and used to tinker with cars. So, I trust he took care of it. He is a friend too.

Here is my situation.

About a week ago my Malfunction Indicator Lamp came on, I went to autozone and the P0420 code in both sections came up.

The previous owner of the car told me thats the same code for the o2 censer that he just had replaced by Honda right before I bought it from him. Thing is, we both drove it about 200 miles after the fix because Honda said it would most likely come on again after the car reconfigures itself. Honda said the problem is probably the CAT and the repairs would be around $1,400(not covered by warranty). The light didn't come back on........ Until I owned the car after driving 700 miles with it.

After researching these forums and countless google searches, I came across some threads that suggest I run the gas tank close to empty, put some fuel system cleaner in, then fill the tank with high premium gas.

I was going on a camping trip so I saw this as a good opportunity to test the theory out, it was 500 mile round trip.
About 50 miles after doing this the light turned off! Sweet, I thought. Then after another 100 miles the next day it came back on. This sucks, I thought. The next day driving home it turned off again, then back on within 100 miles from turning off.

Today I went back to autozone and its the same P0420 code.

Is this normal? Again, car illiterate here. Besides going back to Honda (my warranty is still in the mail being sent to me). Anyone have a reasonably priced solution?

Thanks.

 

Any word on this yet out side the forum?

 

P0420 can be caused by more than the catalytic converter. Usually, P0420 means "Catalyst System Efficiency Below Threshold" which means that the car's computer does not think the catalytic converter is working as well as it should. While the catalytic converter could be bad, one or more of the oxygen sensors may be bad. Oxygen sensors are much cheaper than a catalytic converter ($150 - $200 each). I do not know if that is any help to you, but it is somewhere to start. I doubt your catalytic converter is still under warranty because federal law says that the catalytic converter must be warrantied for 8 years or 80,000 miles. Unfortunately, you are a bit over on the miles.

 

Wouldn't a quick emissions check with a tailpipe sniffer determine whether the cat was bad? Cheaper than changing parts.

 

I got this when I swapped out the cat for a test pipe (whole other subject) but I ran a spark plug defouler, drilled out, and it solved the problem. If the O2 sensor was bad, but you don't want to spend the dough on a replacement, have a mechanic friend put the defouler on. It just spaces out how deep the O2 sensor reads in the exhaust piping.
I occasionally get the 0420 code, but only every 5K miles maybe... haven't had it since end of last year actually.
It could be a cheap way to try and differentiate between the sensor or a bad cat. They're like 5 bucks from autozone, I think 5/8 in. works.

 

Thanks for some info everyone. I just got back from another camping trip, the light turned off! I'm going to hope it stays off for a good while. *knocks on wood*

If the light comes on again I might look into going to the DEQ to get a emissions check for the CAT. It costs $12. I'm just afraid of what might happen if I fail, or by then my warranty might arrive and I'll pay the $100 to see what Honda thinks.

All I'm doing about it in the meantime is filling the car with Premium gas, just glad it turns off sometimes. Anyone think this could be caused by a bad tank of gas? I do remember filling it with regular gas at Shell the night before the light came on.

 

Here's a good summary with links to 02 sensors. Troubleshooting P0420 Catalyst Code

I'm not thinking premium fuel will help. You're seeing an intermittent problem that can be hard to chase down. A stiffer up the pipe could be a good next step.

K_C_

 

I know this is an old thread, but that code looked familiar. It reminded me of a video on youtube on what to do about that code. The guy that does these videos has been a mechanic for over 40 years. His vids are worth a look.

Here is the one he does about code P0420:
YouTube - Fixing Bad Catalytic Converters With Inefficiency Code P0420

 

Ha Scotty Kilmer's now my got to guy! Great find - down home car fixin that works.

 

Bad gas will turn it on.. I had a motorcycle a GMC Van and my Fit's CEL's will light up when I have put Conoco gas in them...

 

P0420 code is a death sentence for Nissan's QR25DE line of engines. For the FIT...don't think so

Any of the following could throw a P0420 code:

- Bad/leaking catalytic converter
- Faulty O2 sensors
- Faulty engine coolant temperature sensor
- Damaged/leaking exhaust manifold
- Retarded spark timing

Probably more than likely a cat, but check the other issues first. Check to see if there are any leaks in the exhaust system first, then move on to the O2 sensors. If I remember correctly, on my Altima the sensor in front of the cat has a fluctuating waveform, and the sensor behind the cat has a more even waveform. Not sure if it is the same for the FIT...

Anything could cause that damn MIL to come on...from a bad tank of gas to forgetting to close your gas filler cap completely.

Good luck!

 

Got the above code & before doing bunch of work including spending money. I disconnect the positive terminal of battery, wait some seconds & reconnect. Wah la the engine light went away. I figure if it's a real issue then it would come back plus the car running fine.

 

...do people also write "like" as much as they say it in conversation, what happened to English grammar and writing in society today...it's an 0420 code for illiteracy 😁