memphistex

I am looking for help on a PO 157 code. From what I read this sensor is the passenger side rear sensor. They also say it could affect gas mileage. They also say you can delete the message. I am confused. If I get it deleted, what will it do to my mileage. This is on a 2001 GMC Sierra 1500 HD 6.0 engine. Thne gas mileage is bad enolugh.

Anyone please.