2001 Boxster s O2 Sensor Question
 

I have an 01 model with 36K miles. The CEL came on recently and the codes read P1126, and P1131. My question, is there a way to tell which of the sensors need replacement either pre or post cat.

Thanks

try the 986 (boxster) area.

p1126 on boxster means the upstream (pre-cat) O2 sensor on cyl4-6 side (driver side) of engine is out of range.

post-cat sensor problem would be a p0420 or p0430

with such low miles i don't think (though certainly not impossible) that the O2 sensor is aleady bad unless you had another problem.
clear the code with a code reader (or battery disconnect to reset ECU) and drive around for a while and see if it comes back.