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Smog test! Code P0420 (Catalyst system below threshold) E350
Hey everyone, so I’m new to posting on here but I have had the issue with code P0420 catalyst system below threshold (bank 1) for a while. I have an E350 W212 (184,000 miles). Does anyone know if that will for sure be the catalytic converters or if anyone has had luck with just replacing O2 sensors? I have my California Star smog due soon and am not sure what to do. The car burns oil a bit like 1/2 quart or so every 1-3k miles. Funny enough I had another Mercedes E350 W212 and it started having the same issue at similar mileage (180k miles). The CEL comes on for about 1k miles goes away and comes back.
let me know if anyone has had similar issues as I know they say Cats go out at this time but I know many cars with Cats still fine with over 250k miles. Thanks!!
Oil burn that much will kill your wide band Lambda sensor ( front ) and the rear oxygen sensor too..................
Your CAT could be borderline clogging, but the reporting quality of the 2 sensors mentioned has gone bye bye and 184K miles is already way too long a service life for those 2 oxygen sensors.
So get them 4 sensors first as you need them anyway.
Go to FCP euro and get direct BOSCH ones, if you go MB ones .... you will have a heart attack at the prices purely from having the STAR logo
Thank you for the reply! So I assumed that half a quart of oil every 2,000 miles is not that bad ? And also in getting new O2 sensors for the front wouldn’t the issue happen again if the car still burns oil ? I might try getting them though and I always buy my stuff from FCP euro! Mercedes want like 350$ per O2 sensor!! But FCP euro don’t seem to have them, I saw Bosch ones on Pelican parts though for like 130$ front O2 and 73$ downstream. Would I need all 4? As thats a lot of money to spend if they are just fine. Thanks again.
Thank you for the reply! So I assumed that half a quart of oil every 2,000 miles is not that bad ? And also in getting new O2 sensors for the front wouldn’t the issue happen again if the car still burns oil ? I might try getting them though and I always buy my stuff from FCP euro! Mercedes want like 350$ per O2 sensor!! But FCP euro don’t seem to have them, I saw Bosch ones on Pelican parts though for like 130$ front O2 and 73$ downstream. Would I need all 4? As thats a lot of money to spend if they are just fine. Thanks again.
On the oil, what kind of oil are you using? How often is your oil service?
On the oil, what kind of oil are you using? How often is your oil service?
depends really, I have used Castro, Mobil 1, and Liqui moly 5W-40 and sometimes 10W-40. I change the oil every 3k-5k miles with a new filter. I do have a small oil pan leak but I’m sure I am still burning oil other than that.
The expensive ones are the FRONT, coz they are wideband AFR. The rear ones are cheap because they are narrow band. Labor to remove exhaust system if you need an Indie will be higher than the narrow band x 2.
I just got it yesterday........yipeee !!! Tax + yada yada 25% of above price. Still CHEAP !!!!!
Well, the only time I burn any oil for 5,000KM of service life was when I took the car for 30+ laps at the track ( 2 different days ) and that was 0.5 liters I needed to add oil.
Never never I ever need to add oil for any 5,000KM oil service life I done so far. Now my car is 38,000KM ish only, but I am brutal and WOT very often.
Your M276 3.5NA oil vapor separator system could be part of the BIGGER culprit, if your piston rings + liners are still OK.
My M276 3.0 Turbo oil vapor separator is much much better, zero oil into my air intake.
The expensive ones are the FRONT, coz they are wideband AFR. The rear ones are cheap because they are narrow band. Labor to remove exhaust system if you need an Indie will be higher than the narrow band x 2.
I just got it yesterday........yipeee !!! Tax + yada yada 25% of above price. Still CHEAP !!!!!
Well, the only time I burn any oil for 5,000KM of service life was when I took the car for 30+ laps at the track ( 2 different days ) and that was 0.5 liters I needed to add oil.
Never never I ever need to add oil for any 5,000KM oil service life I done so far. Now my car is 38,000KM ish only, but I am brutal and WOT very often.
Your M276 3.5NA oil vapor separator system could be part of the BIGGER culprit, if your piston rings + liners are still OK.
My M276 3.0 Turbo oil vapor separator is much much better, zero oil into my air intake.
Have fun..................
Yaa I’ll check it out thanks! The oil crankcase separator was leaking before and had it replaced, I was looking the other day and it seems like it’s leaking again so maybe you’re right, it’s only been like 8 months. I also drive really hard and at 184k miles I’m glad the car is still alive and as well lol.
08-09-2023, 06:39 AM
