P0137 is: 1/2 O2 Sensor Shorted To Ground. That's the right bank downstream sensor. That indicates the sensor output is shorted to ground. Pull the connector off the sensor and measure between pin 4 (TN/WT wire) of the connector and ground. If you don't have a short it's a bad O2 sensor. If you have a short at the conector with it off the sensor, you need to disconnect connector C2 at the PCM(Powertrain Control Module) and see if you still have a short. If it's still there...it's in the wiring somewhere..possibly a frayed wire or pinched or something. If the short goes away with the C2 connector removed..then it's the PCM. I'm assuming you're using your original PCM..so I'd suspect a bad sensor first or something happened to the wiring harness when it was pulled from the donor or on installation. Good luck.