P0420 help needed

hahork · Post by **hahork** » Tue Aug 30, 2011 11:33 am

Sorry for the noob questions- Went to Autozone and got printout for CEL. I've seen a lot of p0420 posts on here, but looking for clarification. Is there a way to know for sure if the problem is O2 sensor (and if so, which one?) or the CC? Does anyone know the approx cost of replacing the CC? Any good mechanics in the Philly area?any help appreciated

keithvibe · Post by **keithvibe** » Tue Aug 30, 2011 8:28 pm

only way to be sure it's the O2 is to use an oscilloscope on it. Any ASE mechanic should know how to use one. But then your paying their hr rate. Most just toss the 80 bucks at the new sensor but then end up getting a new Cat a few months later.

hahork · Post by **hahork** » Tue Aug 30, 2011 10:55 pm

Thanks, guess there's no easy way around this. Has anyone cleared a CEL by cleaning the fuel system?

joatmon · Post by **joatmon** » Wed Aug 31, 2011 11:29 am

What year/mileage vibe do you have? I think the catalytic converter might be covered by the longer emissions warranty.

MarkM04 · Post by **MarkM04** » Wed Aug 31, 2011 9:10 pm

I just got this code to.Since it's supposedly related to the catalytic converter, it should be the second O2 sensor, as the first one is way up on the exhaust manifold.From what I can tell, there's no sure way to diagnose this as either the cat or the o2 sensor. I'm going to try the spark plug anti fouler trick to see if that keeps the CEL off. It's a lot cheaper then an 02, and a heck of a lot cheaper then a cat.

lovemyraffe · Post by **lovemyraffe** » Thu Sep 01, 2011 2:46 am

P0420 could also be related to the intake manifold gasket, MAF...The best way to know for sure is to take it to a mechanic like keithvibe said.

hahork · Post by **hahork** » Thu Sep 01, 2011 3:14 am

sadly, it's an 03 with nearly 140k miles (and up till now, no real problems!)

DiveNut · Post by **DiveNut** » Fri Sep 02, 2011 11:54 pm

Betting it is your CAT. I threw the same code awhile back. 103K on my 2004. I ended up going with a direct fit, Magnaflow piece (part #93200). The local muffler shop knocked it out in 25 minutes while me and my kids waited. Total damage, $222 for the Cat + $75 for the install, $297 total. At least I don't have to stare at that damned CEL now.

MarkM04 · Post by **MarkM04** » Tue Sep 13, 2011 3:51 am

Just to follow up on my anti fouler 02 spacer trick. Before my CEL would come on every 40-100 miles. After the spacer, it hasn't come on yet. It's been about 600 miles. So I think it's not coming bake.I don't have to pass emissions testing, so I'm not sure if your car would pass or not with this mod.

P0420 help needed

P0420 help needed

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