How to Replace an O2 Sensor in a 1999 Sienna

Use an oxygen sensor wrench to replace an oxygen sensor

The emissions control system of most modern vehicles uses an oxygen (O2) sensor to measure the amount of oxygen in the engine exhaust. The sensor transmits this data to the vehicle's computer by means of an electrical wire. The computer then interprets the data and makes adjustments to the air/fuel mixture while the engine is running. This helps the engine operate at peak efficiency, thereby reducing exhaust pollutants. The O2 sensor requires periodic replacement which many owners are able to do themselves.

Things You'll Need

• Penetrating lubricant
• Oxygen sensor socket and ratchet

Instructions

1. Park the vehicle, set the parking brake, shut off the engine, and open the engine hood. Let the engine and exhaust system cool completely before proceeding to avoid burns.

2. Locate the sensor, which is threaded into the exhaust manifold, above the exhaust pipe flange on the front of the engine. Apply some penetrating lubricant to the base of the sensor and let it sit for 30 minutes. This will help loosen the sensor for easier removal.

3. Disconnect the sensor wire by unplugging it from the connector on the vehicle.

4. Back out the sensor by rotating it counterclockwise with the sensor socket and ratchet.

5. Insert the new sensor into the hole and tighten securely with the socket, rotating it clockwise. Attach the sensor wire to the connector on the vehicle.

Tips & Warnings

• Let the engine and exhaust system cool completely before changing the sensor to avoid burns.

References

• Auto Zone: 1999 Toyota SIenna O2 Sensor Location
• Auto Zone: 1999 Toyota Sienna Oxygen Sensor
• Auto Zone: Changing and Oxygen Sensor 1999 Toyota Sienna

Resources

• Auto Zone: Oxygen Sensor Socket