Folks,
P0131 indicates low voltage output from the sensor. Check sensor output at the connection under the left edge of the cosmetic cover above the engine. At that spot my sensor produced output voltage with the engine running, but the OBD code reader watching live data showed 0.00 volts were getting to the ECU, no voltage at all. This indicated a wiring problem between the sensor and the computer. That plastic snap on cover over the engine was rubbing on the wiring harness over the right side of the engine at the edge of that cover. The yellow wire with a red stripe is the one that carries the output voltage from the upstream oxygen sensor. That cover had rubbed through the wiring harness and severed that wire. Patch the wire, trim off the edge of that cover where it rubs, and you should be on your way.