Oxygen Sensor: Testing and Inspection

2002 Toyota Highlander 4WD L4-2.4L (2AZ-FE)SECTION Testing and Inspection




INSPECT HEATER RESISTANCE OF A/F SENSOR (No. 1, No. 4 Cylinder side)
a. Disconnect the A/F sensor connector.

b. Using an ohmmeter, measure the resistance between the terminals +B and HT.
Resistance:
1.8 - 3.4 (Ohm) at 20 °C (68 °F)
5.0 - 7.5 (Ohm) at 500 °C (932 °F)
If the resistance is not as specified, replace the sensor.

c. Reconnect the A/F sensor connector.





INSPECT HEATER RESISTANCE OF A/F SENSOR (No. 2, No. 3 Cylinder side)
a. Disconnect the A/F sensor connector.

b. Using an ohmmeter, measure the resistance between the terminals +B and HT.
Resistance:
1.8 - 3.4 (Ohm) at 20 °C (68 °F)
5.0 - 7.5 (Ohm) at 500 °C (932 °F)
It the resistance is not as specified, replace the sensor.

c. Reconnect the A/F sensor connector.





INSPECT HEATER RESISTANCE OF OXYGEN SENSORS
a. Disconnect the oxygen sensor connector.

b. Using an ohmmeter, measure the resistance between the terminals +B and HT.
Resistance: 11 - 16 (Ohm) at 20°C (68°F)
If the resistance is not as specified, replace the sensor.

c. Reconnect the oxygen sensor connector.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.