how to replace o2 sensor?

i would like to know if replacing the O2 sensor requires a professional help? i am running a 30x9.5x15 on a stockk 2001 cherokee sport. my gas mileage is at 14-15 mpg. i am planning to replace my O2 sensor hoping that it will improve my gas mileage. i am not sure if its bad but i just bought my xj used from a dealer 2 months ago. if somebody could help with a diagram on hot replace myslef, i will be able to save money on the labor. and also, what brand is good and where to purchase it. i will be cahnging the spark plugs too after i change the O2 sensor. thanks a lot!

your milage is about the same as my 99 stock with 80K and the same tire size.
I haven't replaced an O2 on a jeep but have on other vehicles. removing the old, i cut off the wire and got a 1/2" breaker bar with the correct socket and it unscrewed. The new O2, i borrowed a tool that looked like an extended socket with a slot up the side. Helps not damage the wire. Why do you think the O2 sensor has issues? You can take to autozone and they will (in some areas) hook up a scanner and see if any codes are being thrown out. Good luck.

WHICH O2 sensor? Your 2001 has 2, upstream and downstream from the cat.

Like he said, it's not too difficult to change as long as it's not seized up in the bung fitting. You may want to hose is down with a rust penetrant for a few days running before you try and take it out (yes, you want to do this on a COLD pipe.....)

1) disconnect the wiring
2) use a wrench (7/8 i think) to unscrew the old one
3) screw the new one in
4) hook the connector back up

i really dont know if my o2 sensor needs to be replaced? i was browsing some discussions and saw some people having the same tires as mine but they have 18-20 mpg. if i dont have change the o2 sensor, what else should i consider checking/replacing to improve my gas mileage?

Decarbon the engine with product of your choice, Seafoam, BG, GM top end cleaner. Clean the throttle body with a good FI spray cleaner but do it without spraying into the sensors or better yet remove the TB and do it on a work bench. Then run a couple of 20oz cans of Chevron Techron FUEL SYSTEM cleaner NOT Fuel injector cleaner thru the tank.

go to autozone and buy the oem style bosche. its the stock one, just a different number and it comes with a connector on it. Don't get the cheaper one, you have to splice the wires to get it in. If you bring a ratchet with you, they have the loaner 02 sensor sockets to be done right there. just unplug the old one, unscrew the older one, put the new one on and plug it in. don't worry about the 02 sensor after the cat, all it does is detect if the cat is bad or not from what i understand.

RichP said:

Decarbon the engine with product of your choice, Seafoam, BG, GM top end cleaner. Clean the throttle body with a good FI spray cleaner but do it without spraying into the sensors or better yet remove the TB and do it on a work bench. Then run a couple of 20oz cans of Chevron Techron FUEL SYSTEM cleaner NOT Fuel injector cleaner thru the tank.

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Then run a couple of 20oz cans of Chevron Techron FUEL SYSTEM cleaner --- do i pour this into the gas tank? sorry, my first having an xj.