P0420, Bank 1 kitty cat is dirty and isn't working correctly or it thinks at least. Usually means B1 cat needs replacing, but I always verify before condemning. P0137, could be a symptom of a problem upstream with the engine running lean, or could be a faulty sensor. Hint, if you go to replace the O2 sensor, which I would consider before the Cat, do not, let me repeat DO NOT buy a bosch sensor. Use the OE, or an NTK(ngk) sensor.