Replacing Bank 2 Oxygen Sensors

Disclaimer: This is simply a documentation of work I performed on my Xterra. I am not a mechanic therefore any work you do on your own is at your own risk.

Recently, my 2000 Xterra’s “Service Engine Soon” light made an unwelcome appearance on my dash panel. Frustrated, I did some quick research as to what steps I should take regarding the newfound problem. I pulled out the owners manual and found that the SES light wasn’t an emergency unless it was flashing. If the SES light is flashing it can be a sign of major problems and should be driven with caution. Since my SES light was constantly on and my X didn’t exhibit any signs of trouble, some of my worries were relieved. But, that little light drew my attention every time I started the engine. I couldn’t stand it any longer and decided to take action!

First, I found that out that Autozone would test my SES light for free. So, I took them up on the offer and found that my Xterra was showing three error codes:

1. Oxygen Sensor - located at Bank 1, Sensor 1
2. Oxygen Sensor - located at Bank 2, Sensor 2
3. Knock Sensor Problem*

*(NOTE: According to my Nissan dealer almost all Nissan’s have a knock sensor error and they can be ignored for the most part. A knock sensor will not cause your service engine soon light to appear on it’s own. Since replacing 2 oxygen sensors, my service engine soon light has not come back on).

OK, so what does Bank 1 & 2 mean? In Japan, the steering wheel is located on the passenger side. Therefore, Bank 1 is the passenger side of the engine while Bank 2 is our driver’s side. The 2000 Xterra has a total of four oxygen sensors. Two sensors are located before the catalytic converters and the other two are located past the catalytic converters.

Specifically, Bank 1 Sensor 1 is located on the exhaust manifold on the passenger side of the engine inside the engine compartment. Bank 1 Sensor 2 is located underneath the chassis approximately where the passenger’s feet would be located. Bank 2 Sensor 2 is underneath the driver’s feet just opposite of Bank 1 Sensor 2. Bank 2 Sensor 1 seems to be the most difficult to access as it’s mounted between the engine & firewall on the driver’s side of the engine.

At this point I knew I had two oxygen sensors that needed replacing but knew I had a lot of work to do. I purchased both sensors at my local parts store for around $100.00 and decided to give it a try myself since my local Nissan dealer wanted over $300.00 to replace one sensor!

Replacing Bank 2 Sensor 2

I slid under the driver’s side door and located the 02 sensor. Notice there are four wires (two white, one black, one gray) going into the sensor. There’s also a red cable protector which comes in handy when locating the connector inside the engine compartment.

Space is tight while lying on your back under the Xterra. I’ve found the easiest way to change these oxygen sensors is to cut the four wires where they enter the sensor using a pair of diagonal cutting pliers. Obviously, I was 100% committed to changing this sensor or I wouldn’t have cut the wires!








Once the wires are cut I can easily slip an open end wrench over the sensor which makes removing the sensor much easier. The sensor becomes very tight over time with heating & cooling of the exhaust pipe so expect to use some brute force to loosen the sensor. I was unable to loosen the sensor with the open end part of the wrench because it would slip off every time. I also tried a crescent wrench with no success. They do make a special oxygen sensor removal socket you can purchase at most auto parts stores but it wouldn’t fit inside the enclosed area.








Once the sensor is removed the cable to the sensor cable must be taken out. I actually found this to be the most difficult part of the entire process. The cable runs from the oxygen sensor, to two cable clamps on the backside of the engine, and finally on to the engine compartment. I used a long pry bar to brake one zip tie loose that held the cable to the engine. Later I had to pull on the cable to free it from a bracket that held it in place near the side of the transmission.

As you can see below, this connector has the same red cable cover which makes it easy to locate inside the engine compartment. I use a flat head screwdriver to remove the connector from the bracket by forcing the connector forward. Notice the connector is located just above the oil filler cap. The new oxygen sensor reuses the old 02 sensor’s connector. I disconnected the cable and trimmed about 3 inches from end of the cable to make the length correct. I also reused the existing red cable cover to help protect the new 02 sensor.

To summarize the steps I took to replace the oxygen sensor:

1. I cut the 4 wires going into the old oxygen sensor.
2. Then, I used a boxed end wrench to remove the old oxygen sensor.
3. Next, I pried the 02 sensor cable loose from the engine where it was being held in place with cable ties.
4. After everything was removed I wired in the old existing cable connector to the new 02 sensor.
5. I installed the new 02 sensor, plugged in the connector, & zip tied the cable securely into place.

The entire project took about two hours from start to finish. It’s not too technical and in my opinion well worth the effort considering the cost a dealer charges to change a sensor. The tools I used in the project included:

1. A 7/8″ (22mm) open end/boxed end wrench
2. Wire strippers
3. Diagonal Cutters
4. (2) Pry Bars (just to break the cable ties loose for the 02 sensor)
5. Bosh Part # 15727 Oxygen Sensor
6. A cheap tarp just for lying on to keep off the ground

Read more...