[paulv]

Here's some info to start with:

Possible fault causes
1) Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)
2) Valve lift error
3) Aged oxygen sensor behind catalytic converter
4) Catalytic converter faulty (pre-catalytic conversion rate too low)

Doubt that item #1 is the cause unless someone was doing work on the car.

For item #3, try moving the Bank 1 sensor to Bank 2 and see if the fault also moves -- if it does, then the aft bank 1 sensor is defective. Also check wiring as these sensors are low to the ground.

Regards,
paul...