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Toyota Sienna Oxygen Sensor Removal

Making its debut in 1998, the Toyota Sienna has always featured at least three oxygen sensors, due to the employment of its V-engine. A V-engine is shaped like a V and has an exhaust manifold on each side. Two upstream oxygen sensors monitor the fuel to air ratio before the exhaust hits the catalytic converter. Another sensor is installed in or to the rear of the converter to monitor its efficiency. If the Sienna features two converters, there will be four sensors installed on the minivan. One for each manifold and one for each converter.

Finding the Right Sensor

When an oxygen sensor fails, it will trigger the malfunction indicator light (commonly known as the check engine light) on the instrument panel. Either read the diagnostic trouble code (DTC) with a scan tool or have it read at a local auto parts store. Most all scanners will reveal a DTC(s) with a letter and a number. This specific trouble code number can either be revealed with a brief description by the scanner or may have to be looked up in a on-board diagnostic trouble code list.

Any code that reveals a "sensor 1" problem will indicate it is one of the upstream sensors near the manifold. "Sensor 2" codes will reveal the problem is in the downstream sensor near the converter.

Bank locations are trickier, but not overly complicated. To locate "Bank 1, Sensor 1" simply find where the number one, three and five cylinders are on your Sienna. "Bank 2, Sensor 2" would indicate a problem with the downstream sensor on the number two, four and six cylinder side of the engine.

Replacing the Sensor(s)

While its not a bad idea to replace all the sensors when one fails, sometimes its financially burdening. This is where finding the right sensor comes into play. The front and rear sensors are not the same part numbers and are not interchangeable.

To replace the front sensor(s), lift the front end or the entire vehicle to gain access to the undercarriage of the exhaust system. Locate the sensor and disconnect the wire harness. Use a small screwdriver to depress the locking plug connection if necessary.

Next, use a 22mm wrench or an oxygen sensor socket and suitable ratchet. Sometimes on the front sensors, its difficult to get one tool or another onto them, so use what works best for you. Spray the threads of the sensor with a copious amount of lubricant spray, such as WD-40 or PB Blaster and allow it to soak in for a few minutes. Use the wrench or ratchet to loosen the sensor by turning it counterclockwise. A box-end wrench would work best because an open-end wrench could mar the hex-head shape of the sensor. Simply insert the detached wire through the box-end of the wrench before applying it to the hex-head. The oxygen sensor socket uses a slit down the side of the socket that accommodates the wire. Once the sensor is loose enough, finish removing it by hand.

The rear sensors are easier to access than the actual sensor, but Toyota places the plug connection under the carpet beneath the front seats. This requires opening the door and then removing the bottom door trim panel with a screwdriver. Set aside and reach underneath the carpet and towards the floorboard and then under the seat to obtain the plug. Once disconnected there, return to the undercarriage and simply pull the rubber gasket plug out from the floor board of the Sienna. The gasket holds the wire in place and prevents water from getting into the floor of the cab.

Once the wire is released, remove the oxygen sensor as you would have or already did the front ones.

Universal or Direct-Fit

There are two types of replacement sensors. Many companies try to promote the fact that youll save you money by purchasing universal sensors. These sensors require eliminating the plug connection on both sides of the wire harness. Next, match the wire colors up (which do not always match to the OEM wire harness) and butt connect. Since the rear sensors of the Sienna plug underneath the front seat and carpet, remove the seat to get enough room to perform this.

Compare the prices of the direct-fit sensors before deciding to save money with the universal. You might even find the direct-fit ones cheaper or a couple bucks more.