How to replace oxygen sensors...where are they located

follow exhaust system o2 sensors look like spark plugs mounted to the pipe also before and after cat converter

Oxygen sensors monitor the exhaust stream, comparing the oxygen content in it to the oxygen content of ambient air. When oxygen content is low, sensor voltage is high. When oxygen content is high, sensor voltage is low. The voltage created by the sensor is sent to the DME (engine control module) to help maintain a proper fuel mixture. The mixture preparation is used to keep the catalytic converters running at peak efficiency. The oxygen sensors used in E60 models covered in this article has four wires. Two of which are for oxygen sensor heating and two for the signal. The heater is used to get the sensor online faster. Previously, exhaust heat was used. One wire supplied a ground to the sensor for the signal, and the other was for the sensor signal.
Oxygen sensors should be replaced every 100,000 miles. In a perfect world that would be it. Wait until a specified mileage and replace the sensor. However, these sensors fail prematurely, set oxygen sensor fault codes and reduce fuel economy. In this article, I will show you how to identify the location of all four oxygen sensors and how to replace them. You will need an oxygen sensor socket to remove the sensors and remember to always work with a cool exhaust. Oxygen sensors are fragile. Do not drop, as damage may occur. Also, keep the sensor tip clean when reinstalling.
Oxygen sensors are laid out in banks, which refer to cylinders and in sensor numbers referring to before or after the catalytic converter. Bank1 or B1 refers to cylinders 1-3. Bank 2 or B2 refers to cylinders 4-6. Sensor 1 or S1 refers to the sensor before the catalytic converter. Sensor 2 or S2 refers to the sensor after the catalytic converter.
Remember that your car may have been serviced before and parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.
Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.
Figure 1 Bank 1 Sensor 1 is indicated by a yellow arrow. Bank 2 Sensor 1 is pointed out with a green arrow. Large Image ' Extra-Large Image
Figure 2 Bank 1 Sensor 2 has a green arrow. Bank 2 Sensor 2 is shown with a yellow arrow. Large Image ' Extra-Large Image
Figure 3 Replacing sensors before catalytic converter: Oxygen sensors are located in the exhaust manifold. Remove the engine covers. See our tech article on engine covers removing. Locate the oxygen sensor electrical connectors at the right side of the engine above the exhaust manifold. Label or mark the wiring harness to aide during reinstallation. I suggest replacing one sensor at a time so you do not mix up connectors. Using an oxygen sensor socket, loosen the oxygen sensor connection to the exhaust manifold. Do not unscrew yet. Large Image ' Extra-Large Image
Figure 4 Replacing sensors before catalytic converter: Pull the wiring harness out of the mounts (green arrows) along the valve cover. Bank 1 sensor 1 shown, bank 2 sensor 1 is similar. Large Image ' Extra-Large Image
Figure 5 Replacing sensors before catalytic converter: Next, disconnect the electrical connector of the oxygen sensor you are replacing (yellow arrow). First, remove the electrical connector from the mounting bracket (green arrow) by pulling straight up. Once out, disconnect the electrical connector by pressing the release tab and pulling it apart. Note the wiring harness color and the factory sensors color code sensors to help when replacing. Locate the color of the sensor you loosened. Using an oxygen sensor socket, remove the oxygen sensor from the exhaust manifold. Lightly coat the new oxygen sensor thread with anti-seize compound. Install the new oxygen sensor and tighten to 50Nm (37 ft-lb). Then reroute the wiring harness and connect the electrical connector. Repeat if replacing both sensors. Then reassemble the engine covers and clear any engine fault codes using a BMW scan tool. Large Image ' Extra-Large Image
Figure 6 Replacing sensors after catalytic converter: Oxygen sensors are located in the exhaust, behind the catalytic converters. Working below the transmission, remove the transmission splash shield. See our tech article on lower splash shield replacing. Using an oxygen sensor socket, remove the oxygen sensor connection to the exhaust manifold. When reinstalling the sensor, do not allow the harness to remain twisted (green arrow). Be sure it is properly routed and tension free. Large Image ' Extra-Large Image
Figure 7 Replacing sensors after catalytic converter: Next, disconnect the electrical connector of the oxygen sensor you are replacing. First, remove the electrical connector from the mounting bracket (green arrow) by pulling it straight out toward the left side of the engine. Once out, disconnect the electrical connector by pressing the release and pulling it apart (inset). Note the wiring harness color, factory sensors color code sensors to help when replacing. Locate the color of the sensor you loosened. Using an oxygen sensor socket, remove the oxygen sensor from the exhaust manifold. Lightly coat the new oxygen sensor thread with anti-seize compound. Install the new oxygen sensor and tighten it to 50Nm (37 ft-lb). Large Image ' Extra-Large Image
Figure 8 Then reroute the wiring harness and connect the electrical connector. Repeat if replacing both sensors. Then reassemble the engine covers and clear any engine fault codes using a BMW scan tool.

There are at least 3 oxygen sensors. There is one on each side of the exhaust system as the exhaust leaves the engine. These are the upstream sensors. The exhaust then goes to catalytic converters. If you have two, there is a sensor after each one. These are the downstream sensors. Before replacing a sensor, uou should determine if it is bad. Trouble codes indicating problems with the oxygen sensing circuits may have many causes other than a bad sensor. Also be advised that a special socket is needed to remove an oxygen sensor.

Here's a video. Replacing 02 sensor in chevy impala 3 8

Here's a link to your firing order.Bank 1 is cylinder 1,which is on passenger side and sensor 2 is second sensor which is after catalytic converter.Here's the part.

I have written a couple articles that cover subjects including oxygen sensors, oxygen sensor codes, and oxygen sensor locations. I recommend that you read these articles before pending your money on trying to replace any oxygen sensors. Click the links below to see the articles.

What Else Could Be Wrong?

Which Oxygen Sensor Is It?

WELL WHICH OXYGEN YOU REPLACING THE UPSTREAM OXYGEN SENSOR MOUNTED IN EXHAUST MANIFOLD AND THE DOWN STREAM OXYGEN SENSOR LOCATED IN THE EXHAUST SYSTEM AFTER THE CATALYTIC CONVERTER .YOU NEED A OXYGEN SENSOR SOCKET TO REMOVE IT.TO REMOVE OXYGEN SENSOR CRANK VECHICLE TO GET OXYGEN SENSOR HOT BECAUSE HARD TO REMOVE WHEN COLD.BECAREFUL DONT GET BURN ON EXHAUST MANIFOLD WHEN REMOVING OXYGEN SENSOR.AND WHEN INSTALLING NEW OXYGEN SENSOR USE ANTI SEIZE COMPOUND ON SENSOR THREADS.BUT MOST OF THE TIME NEW SENSOR WILL HAVE ANTI SEIZE COMPOUND ON IT.

Hyundai Santa Fe 2001-05
Heated Oxygen Sensor (H02S): The sensors are located in the exhaust system. On some vehicles, one sensor is located up at the exhaust manifold(s) and the other sensor is located down at the catalytic converter. On other vehicles, both sensors are located down at the catalytic converter.



How to Replace an Oxygen Sensor
Parts:
1. Oxygen Sensor
2. Oxygen Sensor

Tools:
1. 3/8 in. Drive Ratchet
2. Multimeter
3. Oxygen Sensor Socket
4. Combination Wrench Set
5. Crimp Tool
6. Socket Set
7. Scan Tool

Steps:
Step 1 * Park the vehicle on a level surface. Set the parking brake and open the hood.
o Tip: Safety Tip:Always wear safety glasses when working on your vehicle. Wear other personal protective equipment (PPE) when necessary, for example latex gloves or safety shoes.
o Tip: Always make sure the struts on the hood can fully support the weight of the hood so that it does not close on you while working. The use of a hood prop can securely hold it in place.

Step 2 * With the engine off and cool, locate the defective oxygen sensor in the exhaust manifold or pipe. If necessary, lift the front of the vehicle and support it with jack stands.
o Tip: Most vehicles have multiple oxygen sensors. How many sensors, depends on the model year and type of engine.

Step 3 * Disconnect the wire connector at the defective oxygen sensor.

Step 4 * Remove the oxygen sensor from the exhaust system.

Step 5 * If you are installing a universal oxygen sensor, cut off the connector from the original sensor and splice the connector wires to the new oxygen sensor. Follow the manufacturer’s instructions supplied with the sensor.

Step 6 * For threaded oxygen sensors, apply anti-seize compound to the threads and install the new sensor.

Step 7 * For flange mounted oxygen sensors, install a new gasket and tighten the mounting bolts.

Step 8 * Reattach the wire connector from the sensor.

Step 9 * If necessary, connect the OBD I/II scanner and erase the fault code.

Hope help with this (remember rated and commented this help) Good luck.

On the SOHC engine the front (A/F) oxygen sensor is located in the front section of the front catalytic converter. The rear oxygen sensor is located in the rear section of the front catalytic converter. On the DOHC engine the front oxygen sensor is located in the front section of the exhaust system, just past the crossover pipe. The rear oxygen sensor is located in the front section of the catalytic converter.

Oxygen sensor location-Baja 2.5L SOHC engine


Oxygen sensor location-Baja 2.5L DOHC engine



On the 2.0L engine the front (A/F) oxygen sensor is located in the front section of the exhaust system, just past the crossover pipe. The rear oxygen sensor is located in the front section of the rear catalytic converter. On the 2.2L engine the front (A/F) oxygen sensor is located in the front section of the front catalytic converter. The rear oxygen sensor is located in the rear section of the rear catalytic converter.

Oxygen sensor location-Impreza 1998-2001 2.2L engine



Oxygen sensor location-Impreza 1998-2002 2.5L SOHC engine

I hope helped with this; remember rated this help. Good luck.

1.The oxygen sensor is located where the manifold comes together and meet the exhaust pipe.
2. The second one would be located after the catalytic converter.
Go to this website and you will see an example.
http://www.walkerproducts.com/locations.html