Emissions schematics o2 sensor location

The post-cat O2 (emissions) sensor reports the exhaust gas condition to the engine management system and it is the pre-cat O2 sensor that closes the loop in the closed loop emission control system.

If the post-cat O2 sensor is reporting bad emissions it is because the pre-cat sensor might be faulty or the engine management system is failing to control fuelling because, perhaps, the injectors are dribbling, the spray patterns are bad, the fuel pressures are wrong or another sensor is sending incorrect information to the system.
It is also possible the CAT is defective or the exhaust or intake is strangled, etc...

the o2 sensor is located by the catalytic converter and anaylyses the exhaust emissions,it may need a tune up but first i'd check all air intake hoses for leaks ,signs of wear etc as if the air/fuel mixture going into engine isn't correct the emissions will not be either ,you can get fuel additives which will clean cylinder,valves and the cat converter so try this first , if the light is still on get the garage to clear the OBD memory and retest drive as a stored code isn't always automaticly erased

The ECU doesn't usually detect muffler issues since they are located beyond the emissions portion (mufflers are essentially for noise not emissions) Mufflers usually have small holes located on the lowest rear-most part to allow condensation to escape. If the holes are big enough for a pencil to fit in, yes you have rusty mufflers. They aren't the problem most likely, but that rust indicates age and poor condition of the entire emissions system. Most issues are in the form of leaks (vaccum or EGR) or sensors O2, MAP or MAF, or you could have a clogged catalytic converter all can be checked by a reputable mechanic if you are overwhelmed.

Hi there:
There is a sensor located before a emission device called a catalytic converter that is located on both sides. The sensors in the back of the engine are called O2 sensor 1 bank one, (sensor before the catalytic converter) and O2 sensor 2 bank one (located after the converter).

On the front of the engine, going down you have two as well for there is a converter on both sides. first one coming from the engine is O2 sensor 1 bank 2 and then your failed one after the converter, O2 sensor 2 bank 2.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day

Hi Santiago:
There is a sensor located before a emission device called a catalytic converter that is located on both sides. The sensors in the back of the engine are called O2 sensor 1 bank one, (sensor before the catalytic converter) and O2 sensor 2 bank one (located after the converter).

On the front of the engine, going down you have two as well for there is a converter on both sides. first one coming from the engine is O2 sensor 1 bank 2 and then your failed one after the converter, O2 sensor 2 bank 2.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day

Modern car engine control systems rely on input from several sensors to regulate the engine's performance as well as its emissions and other vital functions. When these sensors fail to provide accurate information, the driver may experience increased fuel consumption, driveability problems, emission failures, and other problems.

One of the most important sensors in modern cars is the oxygen sensor. Also known as the O2 sensor because O2 is the chemical formula for oxygen, the oxygen sensor monitors how much-unburned oxygen is present in the exhaust as the exhaust exits the engine. By monitoring oxygen levels, the sensor provides a means of measuring fuel mixture.

https://mailordertuner.com/blogs/news/02-sensors-and-why-they-are-important

Ho Joanne:
On Grand Cherokee oxygen sensor locations for 4.0 and 4.7 engines, check this diagrams...







The Oxygen Sensors (O2S) are attached to, and protrude into the vehicle exhaust system. Depending on the emission package, the vehicle may use a total of either 2 or 4 sensors.

Federal Emissions Package (4.0L and 4.7L engines):
Two sensors are used: upstream (referred to as 1/1) and downstream (referred to as 1/2). With this emission package, the upstream sensor (1/1) is located just before the main catalytic convertor. The downstream sensor (1/2) is located just after the main catalytic convertor.


California Emissions Package (4.0L engine):
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the rear/upper upstream sensor (2/1) is located in the exhaust downpipe just before the rear mini-catalytic convertor. The front/upper upstream sensor (1/1) is located in the exhaust downpipe just before the front mini-catalytic convertor. The rear/lower downstream sensor (2/2) is located in the exhaust downpipe just after the rear mini-catalytic convertor, and before the main catalytic convertor. The front/lower downstream sensor (1/2) is located in the exhaust downpipe just after the front mini-catalytic convertor, and before the main catalytic convertor.


California Emissions Package (4.7L engine):
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the right upstream sensor (2/1) is located in the right exhaust downpipe just before the mini-catalytic convertor. The left upstream sensor (1/1) is located in the left exhaust downpipe just before the mini-catalytic convertor. The right downstream sensor (2/2) is located in the right exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor. The left downstream sensor (1/2) is located in the left exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor.

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day.

Your faulty O2 sensor can create EGR problems. Start with just replacing the O2 sensor and see if the rest self corrects.

The Oxygen Sensors (O2S) are attached to, and protrude into the vehicle exhaust system. Depending on the engine or emission package, the vehicle may use a total of either 2 or 4 sensors.
Federal Emission Packages : Two sensors are used: upstream (referred to as 1/1) and downstream (referred to as 1/2). With this emission package, the upstream sensor (1/1) is located just before the main catalytic convertor. The downstream sensor (1/2) is located just after the main catalytic convertor.
California Emission Packages: On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the right upstream sensor (2/1) is located in the right exhaust downpipe just before the mini-catalytic convertor. The left upstream sensor (1/1) is located in the left exhaust downpipe just before the mini-catalytic convertor. The right downstream sensor (2/2) is located in the right exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor. The left downstream sensor (1/2) is located in the left exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor.

The upper O2 sensor is located on the exhaust manifold/s, and the rest is down the line. Some Vehicles have 2, 3, etc. The Upper O2 reads and helps control air/fuel mixture, the lowers usually monitor emissions, and Catalytic converter efficiency.