O2 sensor
 

hello
i have a check engine light in my volvo. i had it scanned and what came up was:

O2 sensor circuit 1
bank 1
exhaust leak
turbo/super overboost condition

i was hoping someone would know which sensor this was. also could the other codes be caused by the faulty o2 sensor?
my car is a 2000 volvo s80, i am not sure which motor exactly. it has the twin turbos

thanks in advance