P0156 fault code

[Mika77]

Hello. 1az-fse engine 2003 t25 avensis auto. Mil light turns on sometimes giving error p0156. Changed bank 2 sensor 2 and also sensor 1. Checked cables ok. Checked connectors ok. Obd scanner shows that sometimes when car cold it takes too much time untils bank2 sensor2 (post cat sensor) starts to read. And mil light comes on. I can see from scanner that bank1 sensor2 starts to read faster(yes from different bank post cat). Both changed sensors oem toyota ones. Car runs fine. Only this frustrating mil light.  I think that i have read the whole internet from car forums about p0156 and nobody knows how to fix or thread has been closed because no answers.  Toyota dealer has told me that maybe cat (1000e plus labor) or ecu (1600e plus labor) or both. Insane prices,welcome to finland 🖒

[m456an]

Have you tried cataclean, you can rule out the o2 sensors.