I recently purchased a 2008 Honda Fit and the day after the check engine light came on. I bought it as is and it was running perfectly. I went to autozone and had a read out of P0420 and low battery. Code was reset and came back on. It has 93k miles on it. So I paid 45 at a local repair shop after it started having intermittent misfires or so it felt at long red lights and when backing up. It only happened at long lights not fast ones. It's barely noticeable most of the time. They say it's a Honda only repair because the computer needs resetting. I brought it to Honda and they said it needs a new CAT. It doesn't include computer update because it didn't say it needed one. The repair cost is $1913. I cannot afford that. This is my work vehicle and I really need it to operate. I don't want to damage the engine by driving like this but I'm not sure what else to do. Could it be something else? Any suggestions? It was previously a 1 owner vehicle that was a trade in on a Benz. Please help.

 

1. The itty bitty fit battery does not last long on average. some have had less than 2 years before failing, if the battery gets week the car goes nuts..
2. if your Plugs have over 45K on them replace them.
3. If the coil packs have over 70 k or so replace them.
4. If the valve adjust has not been done in > 50K do it.
(2,3,4 are service items on the fit ignore Honda... )
5. A can of name brand fuel injection cleaner in the tanks is always a good idea at LEAST 2 times a year.
6. Never trust that a cat is bad without a stand alone gas analizer up the cars tail pipe, plugging in to the ECU is how they sell un-needed cats and O2 sensors, replace the O2 sensors if they have over 125K miles on them, it will pay back over the long haul on fuel and cleaner engine.

 

I agree. Before spending $1900+ I'd hit plugs, coils, battery, O2 sensors, and a valve adjustment. However, I've rarely seen a downstream O2 sensor replacement fix a P0420 code. If it ends up needing a cat, you should shop around at independent exhaust shops. They should be a lot cheaper... especially for a nearly 10 year old car. Good luck! Keep us updated

 

It only has 93,000 miles. It feels more like coils to me than the CAT. I love this little car but I don't wanna pay that much when I just bought it. I have a feeling that isn't even the problem. I was working and hit a deep puddle in a rain storm and a few minutes later the light came on. Could it just be bad timing or could water possibly have harmed a sensor? After I hit the puddle I left it running in park while I delivered an order. Then it came on. I'd rather fix the cheap stuff than the expensive first. I feel like it's running too good to be a major issue.

 

My old Accord (~ 113k miles) set off this code about a year before I sold it and bought my Fit. The car had sat idle for two months, and all sorts of issues popped up when I got back to driving it.
My mechanic did not diagnose anything wrong with the O sensors or the cat. He cleaned out the cat, as it was dirty. I then ran a bottle of CataClean through the gas tank. My MPGs went up by 1.5 miles/gallon. Due for registration, the car passed emissions. The code never reappeared.
I do think the advice on the plugs, coil packs, and valve adjustment is sound.

 

1. The dealer is correct, P0420 is a primary Cat failure.

2. It wont damage the engine. You wont pass emissions though.

3. The only other thing it could be is if the O2 sensor wasn't screwed into the exhaust bung... which would be very obvious visually the O2 sensor would be hanging.

4. Get it fixed by a mom and pop exhaust shop. They will put on a cheapo Cat and it will still cost a lot. Cats are expensive. Magnaflow New York Catalytic Converter 51680 - Read Reviews on Magnaflow New York #51680

 

When you took it to Honda did they actually diagnose the car or did they just go off what you told them and the Code? The code is for the CAT running below operation and basically means it's not working right. I had this same CEL on my Jimmy and ran the car for a year or more with zero issues. Yusuf are not really going to hurt the car, it's just not going to be running the best and you will be burning more gas

 

I know this is an old thread but it's the most relevant and recent one I have found pertaining to my problem. I currently have an 07 fit sport with 223k miles that is throwing codes P0420 and P2647, but the odd thing is the car revs just fine all the way to redline this time instead of cutting out at ~4k like it did last time. Last time I had this code the oil was a little low but this time it's full and still has about 50% life left. I don't want to spend tons of money fixing it but my inspection is due and I need the car so any insight or help would be greatly appreciated.

 

These codes are NOT related. Neither of these codes should put the car in "limp mode" (aka cutting out)

P0420 = Bad Primary (Front) Cat
P2647 = Bad Rocker Arm Oil Pressure Switch or Engine Oil is low