O2 sensor
 

I have a 2003 V6 camry le. And codes p0171, p0174 and p2196 all popped up, they are all related to oxygen sensor B1, S1. Where is that sensor located? There is one clearly in the front of the engine bay and I believe there is one in the back under the intake. Which one is bank 1, sensor 1?

Bank 1 is the engine cylinder bank closest to the firewall. Sensor 1 is the first sensor on the exhaust system coming off the cylinder head. The sensor before the converter.