This is the second time I have had to have the oxygen sensor replaced.... I dont know that it needs replacing till I go for my State Inspection..... it is costly and quite the inconvenience, mainly because of the co$t and that I have to drive the car for 150 miles or so bring the car back and then the place will inspect it!!! WHY is this Oxygen sensor thing keep need replacing?????

 

Do you have a Check Engine light on?


If not, the mechanic is feeding you a line...because a bad sensor (the Jag has 4) will light that engine light EVERY time. "Pending" codes don't predicate a replacement.

 

Exactly, the X-Type has four O2 sensors. Two upper and two lower sensors; one set on each engine bank. Usually it is the upper ones that have to be replaced. The first time you could have had to replace a sensor on Bank 1 and this time on Bank 2, so that is very possible. Like wa3ra said, chances are you have a check engine light on and that will generate a code. Have that code number read and then search on here for that number. or post back and someone will be able to direct you. There are probably threads explaining what it is and how to fix it.

 

The check engine was on, and the mechanic says it wont turn off.... it happened the last time I replace the it, after driving it for a bit the light went off.... now 2 yrs later I am replacing it again...... I am not understanding that there are 4 of these sensors.... I will try and get the code and then research OR maybe just as you guys... Thank you so much for the education !!!

 

Rknight, you have 2 halves of the engine. You can think of it as the side facing the firewall and the side facing the radiator (Jag refers to them as bank 1 and 2). You then have a sensor that is upstream the catalytic converter and one that is downstream on each side. That is where you get the 4 sensors.

The ones between the engine and the catalytic converter is referred to as the upstream sensor. This is basically what the computer uses to adjust the amount of fuel going into the cylinder. If the sensor detects no oxygen, it admits less fuel to the engine. If the sensor detects too much oxygen, then it will admit more fuel. With the computer maintaining the upper sensor in its ideal position, it can then look at the downstream sensor and look at its oxygen level. It should be slightly less than the upstream sensor since there will be a small amount of fuel that is unburnt as it leaves the cylinder and gets burnt in the cat, using up the very small amount of oxygen in the exhaust. The downstream sensor is a true oxygen sensor and is referred to that way. The upstream one gets erroneously called an oxygen sensor, when it is really and air to fuel ratio sensor. They work on very similar principles, but their jobs are dramatically different.

Let us know what the error code(s) that you get and then we can probably point you in the right direction. On the X-Type, normally what goes bad is the heater in the sensor goes out and that will cause it to read wrong, making the computer see the error.

 

thank you.... I was not happy that I had to leave my car overnight. The mechanic said he is trying to understand why the light wont go off.... again, same as last time, you would think they would keep notes or records per car!!! I hopefully will explain what I've learned here on this forum to him.... I will let you know what was said and done... thank you very much !!!

 

There seems to be something missing in this equation. If you have a check engine light on any mechanic should be able to read the code that is causing the light to come on and go from there. Or if there are multiple codes based on the mechanic's knowledge and experience they will address each code in the proper order. Some codes might be triggered by a problem somewhere else. Like your O2 sensor problem. That could be caused by a misfire in the engine in one or more of the cylinders and it could cause the O2 sensor code to be triggered, even though there is nothing wrong with the O2 sensor. Ask the mechanic for the list of current codes you are getting and post them here. From your description it sounds like either the mechanic is not competent to diagnose this issue or you are not fully understanding his explanation. Either way, it probably isn't anything too serious to address.

 

Thank you Alfadude, I fully understand his explanation, because he has no explanation ... he doesn't know "why" ....... I am taking these responses with me when I go this afternoon.... I will be asking for a printout from my last inspection and this one.... altho, I cant cant get an Inspection till I drive the car for many miles (150 ? ) then go back for the Inspection !! Again thank you all !!