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2002 e320 4 Matic Wagon
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Discussion Starter #1
I just cleared these codes on y wagon.
I bought the wagon 18 months ago and the cats had been changed.
Tha car has 180,000 KM.
Any idea what I should check?
Certainly not the cats.
Should I get the O2 sensors changed?
I don"t know if the previous owner had changed the o2 sensors before.
Thanks
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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17,193 Posts
Are the cats the proper ones for the car and how long have they been on there? Hear any rattles when you tap them? Everytime I have had a bad O2 sensor I also had a CEL. How is the car running? Have you noticed that you're getting fewer MPG than before you had the codes?
 

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2001 E320
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151 Posts
hey man...you know you have four cats, eh?...two up front, behind footwells/firewall off exhaust mani...two in the middle, under front seats.... also, check your four o2 sensors, there is one ahead of each cat.... your mechanic can perform a back pressure test at the o2 sensors and figure out if your exhaust is plugged up....good luck!

where are you at? i used to live in toronto ....


here's an old thread.... http://www.benzworld.org/forums/w163-m-class/1328442-error-codes-p0422-p0432.html ......
I finally got round to taking the truck to the dealer this week.
I'd previously cleared the codes(P0422 and P0432 only) - they came back after 2 start/drive cycles - like they're supposed to if the cats are bad.
I checked out the lambda 15A fuse - it was OK.
Using my scanner software I was able to verify that the upstream O2 sensors were tracking the fuel trim (voltage cycling) and both downstream 02 sensors were giving credible steady voltages.
The only conclusion I could draw was that the cats were indeed bad. The confusing thing was there was no rattling and no obvious loss of performance.
I took it to the dealer and explained all of the testing I'd done.
They called me back and said theat my diagnosis was correct - both Catalytic convertors were bad at 78,600 miles - 1400 miles shy of the emmission warranty limit !!
They had to keep the truck one more day as they only had one cat on the shelf.
We got the truck back last night and it appears to be driving OK with no CEL !
The service advisor told me that when they pulled the old cats that the catalyst just crumbled to dust. He also told me that they rarely replace them but they'd just had an E class with the same issue last week.
I find it incredible that both would fail simultaneously and so close to the warranrty limit.
I have a suspicion that the culprit is the ethanol that that is polluting the gas we're being force fed.
I guess I feel lucky that MBUSA picked up the tab but the wife thinks that a Mercedes out of warranty is not worth keeping.
 

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Registered
2002 e320 4 Matic Wagon
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364 Posts
Discussion Starter #4
Are the cats the proper ones for the car and how long have they been on there? Hear any rattles when you tap them? Everytime I have had a bad O2 sensor I also had a CEL. How is the car running? Have you noticed that you're getting fewer MPG than before you had the codes?
They have been changed about 2 years ago.
No rattles.
The car is running perfect.
MPG are A1.
 

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Registered
2002 e320 4 Matic Wagon
Joined
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364 Posts
Discussion Starter #5
hey man...you know you have four cats, eh?...two up front, behind footwells/firewall off exhaust mani...two in the middle, under front seats.... also, check your four o2 sensors, there is one ahead of each cat.... your mechanic can perform a back pressure test at the o2 sensors and figure out if your exhaust is plugged up....good luck!

where are you at? i used to live in toronto ....


here's an old thread.... http://www.benzworld.org/forums/w163-m-class/1328442-error-codes-p0422-p0432.html ......
I guess I'll have to get the backpressure test at o2 sensors.
I am 50 miles awa from Montreal in the Eastern townships where all the ski mountains and golf courses are.
Thanks for the link.
 

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Premium Member
2001 E320 - Brilliant Silver/Ash: 107,000+
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They have been changed about 2 years ago.
No rattles. The car is running perfect. MPG are A1.
Thanks for the additional info. So assuming they are OE (or equivalent) cats, and recently replaced, they should be fine.

I can't remember if there is a test for O2 sensors but one or more might be marginal at that mileage if they are the originals. Remember that Bosch says 100,000 miles lifespan.

The previously mentioned back pressure test can't hurt anything. And both codes ARE pointing toward the cats.

I'm not one of the experts here, but I think I would continue to drive it and check for codes again in a week or so. If any of the O2 sensors is going south you WILL get a CEL in due time. Those could be pending codes because the sensors are not quite out of range enough to trigger a CEL.

Good luck and please keep us posted.
 
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