16805 isn't a code recognized by the bentley manual, a 16804 and 16806 are though, and those codes are saying that the bank 1 cat converter is bad. (passenger's side)

17867
P1459
Exhaust gas temperature sensor 2 range/performance

This means you need to replace the EGT (exhaust gas temperature) sensor, im not so sure if this one is true because if you cat is bad the sensor is gonna get a lot more heat exerted on it causing it to freak out a little bit. I would replace the passenger's side cat (if your code is correct) then clear the codes, i don't believe the EGT fault code will come back.

 

The same 02 sensor code came back a few weeks after replacement, after the EGT and Cat codes (17867 & 16805).

What could be causing the 02 sensor to keep going bad, even though it is the pre-cat sensor, can these codes be related? Or is it likely something else is causing the 02 sensor to go bad (3rd time).

Any ideas Auditech79?