cl55 o2 sensor issue

[3630stephen]

hi peeps i have a cl55 2001 which has been smelling a bit on the rich side so i decided to buy a icarsoft mbii just for diagnostic purposes and tbh it does what it says on the tin so i decided to look at the live data being as no fault codes were showing to find that o2 sensor bank1 sensor2 is showing a constant value of between 0.75 and 0.80v where as the other three were fluctuating as they should so i swapped it out for a bosh direct fit and guess what its still reading the same the only thing i did notice whilst under the car was the secondary cats have been removed i'm not sure how to read the other data so i was wondering if anyone had an idea what might be going on or if there is any other readings i should be looking at with regards to this my current mpg is 9.4 at idle and between 4-8 round town any help appreciated thank you

 

[3630stephen]

okay iv'e been doing a bit of research regarding my little issue and i've come to this conclusion, please correct me if i'm wrong ..... after reading my upstream and downstream readings i started looking at the cats now from what ive read the upstreams should be fluctuating up and down from 0.1 to 0.9 which they both are and the downstream should show little activity if the downstream mirrors the upstream then the cat is dead which is whats happening so when i was getting confused because b1s2 was giving a constant high with little fluctuation between 0.75 and 0.80 which i thought was the duff one is correct and its in fact b2s2 which is mirroring its upstream sensor is still good but pointing me to the fact that the cat is dead

can someone please tell me if i'm going in the right direction before my wife shouts at me for wasting more money