A v-6 or v-8 engine will have two banks. Bank one is the side of the engine with the number 1 cylinder. Bank 2 is the other side of the engine. In your case Bank 1 is cylinders 1-3-5 on the back side of the engine closest to the firewall. Bank 2 is cylinders 2-4-6 on the other side of the engine.
You have two cats bank 1 and bank 2. There are two oxygen sensors before each cat that help determine fuel trim and are refered to as sensor 1 and two oxygen sensors after the cats that monitor cat efficiency and are referred to as sensor 2. The bank 1 sensor 2 O2 sensor is either providing a higher than expected signal or is switching like the sensor 1 O2's. If either of these has occurred the PCM detects that the cat is no longer working as it should and sets the code/turns on the check engine light.
9 times out of 10 it is a cat that has gone bad.
I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa
This means the HO2 (Oxygen) Sensor downstream of the catalytic converter on bank 1, is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
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