Why would you get a p1133 code on a Subaru Outback?

Answer 1

This indicates that your vehicle has an electronic system looking after what is happening to your vehicle.

A mechanic with a properly equipped workshop will be able to give you the answer you are looking for

Or, someone smarter, will give you an answer that it's the O2 sensor. There's a lot of controversy and all seem to agree it's the first sensor.

Interesting, my scanner manual doesn't even list p1133, but the scanner itself lists that code.