Hi everyone first of all let may say im new just joined last night.Ok now that's out of the way i have a question this morning when i started my jeep up the engine light was on drove to auto zone to have it looked at.They plugged in there computer and it said the co2 sensor was bad they said it was the sensor after the cat but i didnt see anything there so before buying it i figured i would ask here if anyone knows what im talking about.Also on my way home the light went off and has not come on again.My question is is the sensor bad,going bad,or does it have anything to do with the fuel injector cleaner i put in last night which by the way is my second bottle i made sure i ran the last fuel with the cleaner run down to 1/8 tank and addded another bottle last night and filled up 89 octane.Also should i use 93 octane or 89 thanks and sorry for all the questions.Tony from NY

 

Do you mean O2 sensor? What year jeep is it?

 

I believe u have 4 O2 sensors, no?.....the code(s) should indicate Bank 1, Bank 2, Sensor 1, Sensor 2, something like that I believe. 87 octane should be good.

 

I'm gonna say that was the issue. Drive it a tank or two and see what happens.

 

Yes 02 sensor 2000 4.0

 

i saw to coming of the manifold going to the exhaust pipe but thats all.

 

Ok i will give it a shot and see what happens thanks for the quick responses everyone .This is my first jeep needed something for all this freaking snow we keep getting my car is terrible in the snow and i woudln't drive it anyway with all this salt on the roads.

 

87 octane is ALL you need for the 4.0. Period.

Save your money from the premium fuels you have been buying, it isn't at all necessary, and it isn't a "treat" for the engine. Octane is simply an anti-knock index.

Keep tabs and see if the code returns.

 

Ok thanks i will use 87 im so use to using 93 it's just routine. I once rented a car for a week and all i kept putting in was 93

 

Here's more on the octane issue. I get asked about it enough that I put together this cut and paste of info.
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The best rule of thumb here is to consult your owners manual. If the manual recommends running regular, run regular. If it is designed for mid grade or premium, run that. The owners manual for the Jeep 4.0 calls for regular gasoline. Running a higher octane than necessary isn’t better for your engine, nor will it result in better gas mileage. Especially the low compression Jeep 4.0. Thinking that you are “treating” your engine by running premium is a long running myth that dies hard.

The AKI (anti-knock index -- also known as "octane rating") of the fuel is an average of two different methods of computing the fuel's ability to resist engine knock. Regular unleaded gas in the U.S. has an anti-knock index of 87, while mid-grade is usually 89, and premium typically is 91 - 93. The higher the number, the more anti-knock protection the fuel offers.

Premium fuel does not necessarily pack more energy content than does regular. Rather, it allows more aggressive engine designs and calibrations that can extract more power from each gallon of gasoline.

The higher AKI (anti knock index) of premium gasoline does not in itself make it any cleaner than regular gas. Oil companies, however, like to advertise that their premium fuels are ‘specially formulated” to clean fuel injectors, restore lost power, cure world hunger, etc. But the truth of the matter is that any “cleaners” that are added to bulk gasoline in the tanker are not going to be present in sufficient quantities to do much good. With the money you save by running the recommended octane of gasoline for your engine, you can afford to put a bottle of quality fuel injector in the tank a couple times a year to help optimize fuel injector spray pattern. The key word here is a “quality” fuel injector cleaner, like BG44K or Techron. Stay away from the el-cheapo fuel injector cleaners that you see lining the shelves of the parts stores. They really don’t work well.

How much will you save by running regular? That depends but for an average driver, you can save up to $200 a year. Gasoline retailers and refiners like to sell high-test premium fuels because it's more profitable than regular grade gas is. The retailer paid about 8 cents more for the premium you pay 15-20 cents more for — though that margin can swing wildly. Refiners make a few cents a gallon more on premium than on regular when they sell to wholesale distributors.

 

So the check engine light came on again so took it again to a different auto zone they plugged in there machine and the same code came up o2 sensor i think bank 2 sensor 2 it's the one after the cat only problem is that there is nothing there the only sensors i have are 2 that come off the manifold pipe. That's it i looked everywhere any help would be great.Also if someone has a pic of the sensor and where it goes after the cat would be a big help theres no spot for it no wires nothing is something wrong or is there computer wrong

 

Bump