Even if your engine is transversely mounted, the bank does not have anything to do with where it is located, be it at the front or the back. There is a bank 1 and a bank 2 when it comes to the number of cylinders in the engine, bank 1 having one and bank 2 having two. A front O2 sensor, a rear O2 sensor, or a combination of both is what tells us if it's the front or rear sensor.