02 grand prix trouble code po137

trouble code reads bank 1 sensor 2 low voltage has been explained to me as left side exhaust second one back. but i can only find 2 sensor one is center of block were exhaust manifolds meet by fire wall the second is located behind the catalytic converter.
Seeing these are both in center line of car i can only assume that bank 1 sensor 2 is the one behind the catalytic converter
Can any one confirm this

Yes - H02 sensor 2 is after the catalytic converter.

right on thanks at least that one easer to get at

these cars only have one pre and one post converter oxygen sensor, so the bank 1/bank 2 doesn't apply. This is the way that many generic OBDII scan tools read these vehicles.