I have the P420 error code and it's been on for probably 9 months but I need to pass inspection.

I have had to buy a catalytic converter 2 years in a row just to pass inspection. I have this same problem popping up every year. I think it might be bad O2 sensors??

Are they easy enough to replace yourself and does this sound like a logical explanation? I went searching through the forum and I think I might be correct but not positive.

 

O2 sensors are not lasting very long these days.
I have gone thr several.
IMO - I blame ethanol.
DIY is easy iff you can get to it ..
But note the code is for the cat system
http://www..com/cr/errorcodes.html
P0420

11-186

11-167

Catalyst System Efficiency Below Threshold

P0420

11-186

11-167

Catalyst System Efficiency Below Threshold

 

cleaned the egr port and passage system of the intake manifold yet?
99s only have 1 egr port and will clog in 75kmiles

run 91 or higher gas all the time? lower is bad for the cat
do you race the car --drive at 100 for extended periods? abuse the cat?
I mean the convertor not your house cat

there is an electrical test for the O2 sensor- but a 99, I would get one just based on age/miles..it cant hurt

Buy DENSO brand at parts store,,its the OE supplier of this part, so plug and play.
Do and ECU reset by clock fuse method to clear the codes and start fresh

 

You really shouldn't have to replace a cat in one year.

I would change the O2 sensors. They are really easy to change.

Also, I have this same code. For emissions you can pull the clock fuse and it will clear the code. Then drive it 60 miles and if the CEL doesn't come back on stop and get the emissions checked.

This is how I did it. I had the same code and it typically took 3 to 4 tanks of gas before the CEL would come back on.

 

Are you aware that all aftermarket convertors must meet epa performance standards for 25,000 miles? Any warranty left?

 

how much are the o2 sensors and what is the oem brand or does it matter??

 

DENSO brand,,these are the OE direct plug/connect and play
most local parts stores carry them
call or look up prices online for whatever store is near you

suggest O2 sensor removal/install tool --buy at same place

 

does it hurt to just change both sensor it's just a personal feeling of knowing that both are new and that phase of my car is done..any thoughts on that.

 

only thing it hurts is your wallet.

 

x1 I'm feeling it these few months, got the same p0420 on my Odyssey, installing another cat this weekend, hope to fix the issue.

 

^^ANOTHER cat? How long did the last one go? No warranty left? If you aren't still under warranty and the car runs fine, I'd get a spark plug non-fouler for the rear o2 sensor.

 

^^didn't meant 'another', just a replacement cat. I think the one on the car is original. Thought of the fouler, but need to do a smog and i think the sniffer in the tail pipe will fail the smog if even with the non-fouler.

Got a 49 State cat off ebay, giving it a try see if it will work, since non-carb. LOL

 

Don't use aftermarket catalytic converters. There's a reason for a several hundred dollars in price difference between the two (aftermarket vs oem). Generally speaking, alot of aftermarket catalytic converters are made using less rare/precious metals then an oem. These metals (due to very low amounts) have a tendency to be burned out MUCH quicker then usual. In my profession, i see this all the time. You would honestly be much better off using a low mileage used oem converter then buying that junk.

BEFORE assuming that these catalytic converters are actually going bad, most exhaust shops will do a quick simple test that involves 2 things: determining if the components is superheating the exhaust gases passing through by measuring temps before and after. And two, using a special vacuum gauge to see if the core is being contaminated with foreign material (oil, coolant, etc...) by measuring pressure differences before and after. Also, inspecting the cat after its removed can pretty much tell you this as well.

If its found that the catalytic converters being removed all still good, most cases end up being a "post-converter" oxygen sensor thats primary duty is to monitor the effectiveness and performance of the converter. If these O2 sensors go bad or even marginally bad, they can give false codes (like P0420) and really mess with your head.

 

If it didn't get caught on the visual inspection, you would very likely pass a tailpipe test with your oe convertor and a non fouler. My gut feeling is that your chances would be better with your oe convertor than an aftermarket one, especially a non california spec. A couple other things to try are: do several wide open throttle accelerations after a 10 minute highway cruise. Follow up with 10 more minutes on the highway. Try a good fuel system cleaner. I like bg44k, redline has a good reputation, techron used to be a good product, but it comes in too many concentrations/formulations for me to keep track of. Sea foam is also good, I don't think it's as aggressive as bg or redline. Do the w.o.t. accelerations drill with the cleaner in the tank.
Beyond that, I think the best order to follow is is professional injection /induction cleaning, front o2 sensor, rear o2 sensor, aftermarket cat, oe cat. At any point in this sequence you can go directly to non-fouler or oe cat with comparable results.

 

I've aftermarket on my Toyota truck when someone stole it and it passed smog, and someone i know also put an aftermarket cat on his Odyssey also passed.

My CEL been on for more than a year, so let see what happen when my Odyssey is due for smog sometime this year, if work.. Hooray.If not, then i guess lesson learn, then i'll try non-fouler with my oe.