The 2003 Toyota Tacoma and similar vehicles use two heated oxygen sensors. The sensors do not work properly until they come up to engine operating temperature. Since the oxygen sensors are heated, they come up to the temperature needed for closed loop operation much sooner than if you were to wait for the engine to heat up, to begin steps on how to replace an oxygen sensor for 2003 Toyota Tacoma.
Common Things That Affect an Oxygen Sensor
The most common things that might cause an oxygen sensor to light up the check engine light are bad spark plugs, bad plug wires, a malfunctioning fuel injector. Several other things may affect the mixture of air and fuel, thus causing excess oxygen in the exhaust. Before you condemn the oxygen sensor, ensure that everything else on the vehicle is working properly.
Tools You Need
Several tools are required to complete this job. If you do not have a specific tool, you can find it at most auto parts store.
Floor jack Jack stands Ohmmeter Oxygen sensor sockets Anti-seize compound Torque wrench
Testing
Two engines were used in the 2003 Toyota Tacoma, according to parts retailer Auto Zone: the 2RZ-FE and the 3RZ-FE engines. The process for testing the oxygen sensors for both engines is the same.
Jack up the vehicle, then unplug the oxygen sensor connector. Measure the distance between the battery positive terminal and the HT terminal at the connector, on the oxygen sensor side.
The connector is square – hold it so the side with no tangs is to the left, and the side with three tangs is at the top. The battery positive terminal is the terminal on the top left, and the HT terminal is on the top right.
If the resistance is not between 11 and 16 ohms at 68 degrees Fahrenheit – it may be a bit higher or lower, depending on the temperature – replace the oxygen sensor that is giving you problems. Reconnect the oxygen sensor, then, if necessary, proceed with the steps to replace the oxygen sensor for the 2003 Toyota Tacoma and similar models.
Replacement
Unplug the oxygen sensor if you plugged it back in after testing it. Remove the sensor, using the oxygen sensor wrench, but turning it counter-clockwise – the oxygen sensors are in the exhaust. One is before the catalytic converter and the other is just after.
Clean the threads in the exhaust. Apply anti-seize compound to the threads of the new oxygen sensor. Screw the sensor in by hand as far as you can.
Tighten the oxygen sensor to 14 foot-pounds of torque. Plug the wiring harness connector in, ensuring that it snaps into place. Ensure that the wires are not touching the exhaust and cannot fall onto the exhaust. Lower the vehicle off the jack stands, using the floor jack.
Celica Oxygen Sensor Replacement
The Toyota Celica uses the same steps to replace an oxygen sensor for 2003 Toyota Tacoma and similar models. The one difference is that the Celica’s oxygen sensors are located in the exhaust in the engine compartment while the Tacoma is rear’s rear wheel drive configuration. Repeat the same process for replacement.
Conclusion
If you get an oxygen sensor code on the diagnostic scanner, before replacing it, ensure that the ignition — spark plugs, wires, cap and rotor — are all working properly. Also, make sure the fuel pressure is correct and that the injectors are working properly. Anything that affects the mixture of air and fuel can cause the computer to store an oxygen sensor code.