I replaced my O2 sensor as standard maintenence so I wasnt getting a code.

I didnt disconnect the battery when I did it so will the computer automatically learn that there is a new O2 in there?

Is there anything I need to reset?

The original sensor had about 145k on it and I was expecting a mileage increase when I put my new one in, but still the same. Around 15mpg's

 

was there a check engine light on?

 

No check engine light.

 

Take the NEG terminal off the battery for like 20 mins (I usually click the key to ON to get anything left in the system out). Then put it back on. All done.

 

I actually read on some other Jeep forum to pull the positive cable and hold it to the neg for 30 seconds and then reinstall.

Turn the key to the ON position and turnheadlights on and then off than turn the key off.

It was for a YJ, but he said it was the same for all Jeeps.

Here it is

http://www.jeeps-offroad.com/f41/com...eset-ecu-6026/