My check engine light is on. The codes are:

PO134 O2 Sensor Ckt No Activity (Bank One Sensor One)
PO400 EGR Flow Malfunction
PO441 Evap Emission Control System Purge Flow Fault

Any suggestions as to what I now need to fix would be appreciated. Cleared the codes and the Check Engine Light was off for a few hours but it came back on. If the O2 sensor needs to be replaced, which one of the four is this code about?

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• 2001 E320

I think you only have 2 sensors.
Sensor 1 is the one in FRONT of the catalytic converter.
Do a search on the EGR & EVAP codes.
There is lots of information on these.

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2007 C 230 Sport.

I know that there are two O2 sensors required after the catalyst and I think that they may be two in the manifold/exhaust pipe before the catalyst. I always use the search function before posting a question and find a lot of very useful information. Can someone confirm the 02 sensor causing the code?

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• 2001 E320

both purge and egr can bring on a O2 code, so address those first..
Purge prob just need cleaning, and egr test are simple with a hand vac , do egr test searech

Thanks Arthur. I know about the EGR valve. Where is the Purge part that may need cleaning?

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• 2001 E320

Purge is on driver fender well area.
It has a fairly large vac line coming to it from the engine . It says MOT on top,
When eng is warm , place it in your hand and you should feel it vibrating @ 5/6 times a sec.. Feels like a hearbeat.
They get crap in them and stick.. a trick is to take the line off between the purge and canister and fill it with a few squirts of WD40, rehook it up and the engine vac will suck it through . cleaning the valve in the process...