Technical The oxygen sensor

[Chelsawy]

Hi there ,
where is the oxygen sensor in the exhaust system , is it before or after the catalytic converter ? and how can i check that it is working perfectly ?

 

[T14086]

before the cat or if your car is EOBD it will have one after the cat aswell which has the sole purpose of monitoring the efficency of the cat.

best way to check is with a oscilliscope.