Lambda sensor driving me mad.

[putbinoot]

Ok people am i going mad, had a check engine light so scanned car and got G3/2 upstream open circuit, now this is my first mistake i did not come here and ask first i looked at a picture on line that had a v6 showing two exhausts and 4 sensors so i ordered 2 upstream sensors thought might as well do both. Get under car to find only one exhaust and what looks like a downstream sensor anyway take it out put new one in and cleared fault which lasted an hour then came back with thrust value to high so i'm assuming the sensor i got is wrong one. So to the point finally i have a 2007 E320cdi 3.0 v6 with what appears to be only one sensor and its after the cat but every where i look it only mentions sensors before cat did they change it on the face lift am i going mad. Sensor i took of has part number 0258017016, has anyone changed there's and found what i have. Thanks for any input.

 

[Boygould]

I have a current fault on a facelift 2007 320 and have ordered that exact Bosch part. There is a sensor upstream of the Cat which is accessible from the bonnet, its on the LHS under the air filter.
I am planning to change mine in the next week or so and looking at the instructions the only issue will be limited room for hands/spanners.

 

[OneForTheRoad]

Its the petrol that has lots of sensors. The derv has only 1.

 

[Boygould]

I have just tried to locate/replace the O2 sensor according to the Star instructions (attached). Once I had pulled things to bits, I found that this is not the case and it appears to be DOWNSTREAM of the Cat under the car! I also checked what star says for other OM642 cars and it seems it quotes upstream sensors as being under the bonnet.
Ran out of time tonight so will need to tackle again. Aggh.

 

[putbinoot]

I have just tried to locate/replace the O2 sensor according to the Star instructions (attached). Once I had pulled things to bits, I found that this is not the case and it appears to be DOWNSTREAM of the Cat under the car! I also checked what star says for other OM642 cars and it seems it quotes upstream sensors as being under the bonnet.
Ran out of time tonight so will need to tackle again. Aggh.

I had a thought that on left hand drive cars it may be at the top but on right hand drive cars the streering shaft is in the way so it is mounted downstream. Once you get under the car and remove cover you can see it right below the cat.

 

[Boygould]

Yes. Managed to get it on the ramps and it was a 1/2hr job (much easier). All done now and the car is much smoother and appears to be giving better fuel consumption... even the wife noticed it!
So in answer to the OP. Yes only one O2 sensor which is DOWNSTREAM of the Cat, accessible from underneath the car once the gear box undertray is removed. Bosch part works well and I paid £70, MB wanted £250 (and prob a bosch part anyway).