1999 Lexus Es 300, P0125,0171,1153, 1155

[bstone77]

1999 lexus ES 300, Repeated Problems with P0125,0171,1153 pending, 1155 pending has had bank 2 sensor 1 replaced twice within past month dealership suggesting ecu replacement but doesn't say why, what/how do I troubleshoot further, ie check ecm, check wiring to sensors, any advice would be appreciated as I have a feeling they've installed two bad sensors or the culprit is hiding elsewhere.