Help me! Code P2A00 Oxygen sensor circuit range/performance bank 1 Sensor 1 2008 honda Crv ex?

I have an 2008 Honda crv Ex and this code came up "Code "P2A00"
Oxygen sensor
circuit range/performance bank 1
Sensor 1 i want to replace it myself because i know its simple and the dealer wants to charge me over $300 and i can do it for half the cost when i looked it, it has two sensors together one closer to the engine and the other a bit more behind it i don't know with of the two it is.

Closest to the engine. It could be something else causing it though,
Burnt, broken, or disconnected wiring and/or connectors
Engine misfires Vacuum leaks
Bad mass air flow or manifold absolute pressure sensor
Engine exhaust leaks

Read more at:
Copyright OBD-Codes.com

If it's a 4 cylinder motor Bank 1 Sensor 1 is the 02 sensor nearest the motor.