How to Replace an O2 Sensor on a 2003 Toyota Tundra

by Robert Moore

The 2003 Toyota Tundra came standard with a 3.4-liter six-cylinder and a five-speed manual transmission. To meet federal emissions standards Toyota placed an oxygen sensor before and after the catalytic converter on the left and right exhaust piping. The upstream oxygen sensors are located on the lower base of the left and right exhaust manifolds, while the downstream oxygen sensors are located at the exit pipe of the catalytic converter on the left and right exhaust pipes.


Step 1

Park the truck on a level surface and set the parking brake. Lift the hood and support it with the hood prop rod. Allow the engine to cool completely before continuing.

Step 2

Lift the front of the truck into the air with a floor jack and place jack stands under the front frame rails. Lower the floor jack until the truck rests securely on the jack stands. Follow the exhaust manifold toward the fire wall on either side of the engine bay to locate the upstream oxygen sensors. Follow the oxygen sensor pigtail to where it connects to the engine wiring harness. Squeeze the locking tab and separate the connectors, if replacing either upstream oxygen sensor.

Step 3

Lie down under the truck and position yourself just behind the front wheels. Look at the exit points of the catalytic converter to locate the downstream oxygen sensors on the left or right exhaust pipe. Follow the pigtail to its connection at the vehicle wiring harness near the transmission. Squeeze the locking tab and separate the connectors for either sensor, if replacing the downstream oxygen sensors.

Step 4

Install the oxygen sensor socket over the oxygen sensor so the pigtail extends through the opening in the side of the socket. Position the ratchet onto the socket and rotate the sensor counterclockwise to remove the sensor from the exhaust piping or exhaust manifold. Apply heat to the piping or manifold around the base of the oxygen sensor with the propane torch if the sensor is hard to loosen.

Remove the oxygen sensor socket and ratchet. Remove the oxygen sensor by hand.


Step 1

Compare the old oxygen sensor to the new sensor. Pay special attention to the connector and length of the pigtail; the sensors should be identical. Inspect the threads of the new oxygen sensor and apply copper anti-seize to the threads if not pre-applied from the factory.

Step 2

Thread the oxygen sensor into the exhaust piping or manifold by hand. Install the oxygen sensor socket over the oxygen sensor; directing the pigtail through the opening. Tighten the oxygen sensor to 28 foot-pounds with a torque wrench. Remove the oxygen sensor socket.

Step 3

Connect the oxygen sensor pigtail to the wiring harness near the transmission, if either downstream oxygen sensor was replaced. Connect the upstream oxygen sensor pigtail to the engine wiring harness under the hood, if either upstream sensor was replaced.

Lift the front of the truck off the jack stands and remove the jack stands. Lower the truck to the ground. Shut the hood. Start the engine and clear any associated trouble codes.

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