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Discussion Starter #1
I have an '03 E320 with check engine light on. Took it in to my local indi shop and was told it was the oxygen sensors (yeah, both?!?!) Anyway, trying to find exactly which is the correct sensors to buy, in that there seems to be all kinds available. Any part number or link would be greatly appreciated.

Car running a bit rough at times. Is there anything other than sensors I should replace? Close to 100K miles and car has gone through both cat's already. Makes me a little suspicious.

Thanks in advance!!!
 

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2003 E320 - wife's car now; 07 Porsche Boxster S - my car!!
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637 Posts
............ Close to 100K miles and car has gone through both cat's already. ......................
You've already replaced both cats in the car already? Anyway, I buy my parts from a dealer who supports another forum. Try Rob Lewis at 513-870-1030 and tell him you're a member of MBWorld forum. He can use your VIN to identify the correct O2 sensors you need. Also, if you get a chance, go to a place like Autozone and have them read the codes and freeze frame data and post it here.

Regards,
paul...
 

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Discussion Starter #3
Have the car at the local Dealer now, in that my indi shop told me that the cat that was just replaced sounds bad. Diesel noise.

Dealer is insistent that the cat is fine and wanted to do their own diagnostics (to the tune of another $180 or so) so I called my indi and had him give me the codes. PO154, PO134 and PO400.

Either way, looks like dealer is doing a "cats fine" stance, so back to the indi I go to have the O2's done I guess. $700.00 though. YIKES!

BTW, Foreign Car Repairs & Sales in Inglwood, Ca., Great shop! Know there stuff!!! Ask for Berney!!
 

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2003 E320 - wife's car now; 07 Porsche Boxster S - my car!!
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..................

Dealer is insistent that the cat is fine and wanted to do their own diagnostics (to the tune of another $180 or so) so I called my indi and had him give me the codes. PO154, PO134 and PO400.

...............
What was the disposition of P0400 (which is an EGR code)?

Regards,
paul...
 

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'07 GL320CDI
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Bad MAF sensor can generate a bad O2 sensor code.

That is, it's not always the O2 sensor.

ALL 320s came from factory with not-so-good MAF sensors and yours should likely have been replaced by now.

In addition, Paulv is correct--0400 code has nothing to do with either and will not be fixed by either MAF or O2 sensor replacement (or both).

IMHO it is futile to have independent mechanics attempt to diagnose these problems unless they have VERY recent Mercedes factory training. Unless you've got one of those, you're better off at a Mercedes dealer.
 

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'11 C350
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I recently replaced all 4 O2 sensors on my '03. The direct connection part numbers for the post cat was not accurate, I ended up splicing the old plug to the new sensor. This is a very simple procedure, was quoted $1400 by the dealer and spent $350 buying parts. Lift ramps and a socket were another $60. Took about 2 hours total, with no prior experience. Bosch makes the sensors and their web site has a good parts number look up. Local big parts store (Pep Boys)had them in stock.
 
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