po155 code on 2004 Chevrolet Blazer

getting a PO155 code, already chanced oxy sensor, what could it possibly be

Asked by for the 2004 Chevrolet Blazer
1 answer
The other O2 sensor??
Which one did you change? The P0155 s for the B2S1 - Bank 2 , the O2 sensor before the catalytic converter.