Clio 172, rear o2 sensor affect fuelling/running?

[Jonnycressey]

Ive just bought a new sensor for my car costing £70 and now been told that the second sensor doesnt affect the cars running etc and is only there to trigger your EML is this true ill send it back if so

 

[MicKPM]

The post-CAT sensor is indeed there purely as a monitoring device to check the efficiency of the cars CAT function. It does not have any control over the vehicles fueling as this is all done by the pre-CAT sensor.

 

[martynzs]

Might worth swapping out the pre-cat one as you have a new one, wouldn't hurt (assuming it hasn't been done recently)

Am I correct in thinking they are the same part?