Nismo is now throwing P0139 P0138 and P0137.

26k miles, droven gently (mostly) since I've had it.

stock cats, no mods other than wheels.

Car runs perfectly normal, SES just kicked on, when I was driving into work today.

These are the possible causes that the codes read

"Open or short circuit condition" x 3
"Poor electrical connection" x 2
"High fuel pressure or leaking injector"
"Low fuel pressure or blocked injector"
Large vacuum leak"
"Faulty heated oxygen sensor bank 1 sensor 2" x 2

Any ideas?

 

Your having a problem with bank 1 oxygen sensor after the cat. Easiest thing is reset the code and swap both rear oxygen sensors and see if it changes to bank 2. Your car is under warranty though so can take it to the dealer. The dealer will try to rape you of course.

 

Only have powertrain though.
Everything else is expired, its an '08.
Any guides around here on O2 sensor replacement?

 

Its ridiculously easy. 7/8th wrench or O2 socket to remove each one and just unplug it. Worst part is sometimes then can be siezed from rust.

Also its part of the powertrain and emissions parts are warrantied for 8 yrs or 80k miles or some ****, I think.