OBDII Code P0153

I have 04 tacoma 2.4l with check engine light on and off.

P0153 02 Sensor Circuit Slow Response (Bank 2 Sensor 1)

I'm wondering if o2 sensor is covered under
"8 YEAR / 80,000 MILES FEDERAL EMISSION AND PERFORMANCE WARRANTY"

The mechanic said that I might want to clean the sensor before replace the sensor, and he would charge $40 for clean and $190 for the replacement.

Is it worth to clean and see if the light goes off for good or just replace it?

Thanks