My check engine light has come on recently; 1999 DISCO II Bosch engine w/134K . The OBDII code reader flashed the following codes: P1174 and P1171; system too rich bank 1 and system too rich bank 2. Note: codes were cleared but came back on with 20+/- miles of driving. MAF sensor is new; just had fuel injector cleaning service; O2 sensors never changed. Last dealer service was around 100K. Looking for guidance as to my next step.

 

I show the 1171 as a lean run on banks A and B, 1174 I can't find.
IO would say based on your mileage that the 02 sensors need to be replaced for sure.

 

1174 is lamda sensor bank 2 max value. This deals with O2. I agree with mike start with four new sensors