On the 2006 Toyota Sienna, the “Sensor 2’s” (aka “Downstream”) sensors are NOT A/F Sensors. They are “Heated Oxygen Sensors“. Only the “Sensor 1’s” (aka “upstream”) Sensors are A/F (Air/Fuel Ratio) Sensors. So… with the P0057, this is pointing to a fault with the internal heater for the Bank2 Sensor2 Oxygen Sensor. The on-board computer uses this internal heater to get the sensor to normal operating temps within a matter of seconds on cold starts. When it tries to activate the heater and sees no response, the P0057 is set. Carefully inspect the electrical connector and as far up the harness as you can looking for any loose, broken or damaged wires. If the visual inspection checks ok, replacing the sensor should sovle the problem. You can find Bank2 Sensor2 located on the side of the engine closest to the front of the vehicle, mounted to the exhaust below the Converter.
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