How to test A/F Air Fuel Ratio Sensor 2000-2007 Toyota Highlander V6

INSPECT HEATER RESISTANCE OF A/F SENSORS 

1. Disconnect the A/F sensor connector.
2. Using an ohmmeter, measure the resistance between the terminals +B and HT.

Resistance:
0.8 - 1.4 ohms at 20 °C (68 °F)
1.8 - 3.2 ohms at 800 °C (1,472 °F)

If the resistance is not as specified, replace the sensor.