I believe if you look through the following that the 2.4L Outlander should have the same number of oxygen sensors and same general location.

http://www.mitsubishi-forums.com/77...nder/46627-mitsubishi-outlander-workshop-manual-1st-generation-2003-2006-a.html

 

figured it out for my 2.4 ...
the oxygen sensor locations for my 4 cylinder Galant 4G69 2.4L engine


bank 1 o2 sensor 1 - ( upstream ) - passenger side upper o2 sensor BEFORE the catalytic converter
bank 1 o2 sensor 2 - ( downstream ) - passenger side lower o2 sensor on or after the catalytic converter

bank 2 o2 sensor 1 - ( upstream ) - driver side upper o2 sensor BEFORE the catalytic converter
bank 2 o2 sensor 2 - ( downstream ) - driver side lower o2 sensor on or after the catalytic converter


hope this helps others, took me like a hour of research to figure this out, was all confusing with the downstream uppe r lower banks and all this terminology that they use that all means the same thing but different ways of saying it.

 

follow up:
sadly to say replacing my oxygen sensors didnt work and i found out my catalytic converters were bad and as soon as i replaced my catalytic converters (the main one thats part of the headers (this has 2 cat) and the 3rd one under the car (this 3rd one clogged from the deposits of the 1st 2 going bad) i was able to clear P0431 code. i went the cheap route and ordered online the main 2 main catalytic converters (the all in one unit with the headers) and the 3rd one i just cleared myself since the smog people dont check it. i personally dont see the point of the third.