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  1. #1
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    Default 1998 XJ 4.0L 02 Sensor question

    Hi I put my jeep on a code reader and it says (02 Heater Circuit Sensor) I was just curious as to which 02 sensor that would be?? Before I go buying and replacing the wrong one... I'm getting very poor gas mileage.. I'm only running 31/10.50s and I'm getting like 9MPG which is sad considering my brother in law has the same jeep except his has an 8 inch lift with 35s and he gets like 14mpg and we both drive about the same.. He's a little more wide open then me.. But please help.. And if you could help with other stuff causing vet bad mpg lemme know!
    Thanks!
    -Jared

  2. #2
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    Default Re: 1998 XJ 4.0L 02 Sensor question

    Quote Originally Posted by Jbaker View Post
    Hi I put my jeep on a code reader and it says (02 Heater Circuit Sensor) I was just curious as to which 02 sensor that would be?? Before I go buying and replacing the wrong one... I'm getting very poor gas mileage.. I'm only running 31/10.50s and I'm getting like 9MPG which is sad considering my brother in law has the same jeep except his has an 8 inch lift with 35s and he gets like 14mpg and we both drive about the same.. He's a little more wide open then me.. But please help.. And if you could help with other stuff causing vet bad mpg lemme know!
    Thanks!
    -Jared
    The O2 sensor closest to your engine has more to do with mpg than the other. Hows the cable?

  3. #3
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    Default Re: 1998 XJ 4.0L 02 Sensor question

    Whats the actual code that you got ?

    You could have a heater circuit fault because the,

    ... fuse is dodgy,
    ... wiring is shorted ... to either sensor,
    ... either of the two sensors are faulty.
    I hate watching simplicity and reliability being ruined by bureaucracy and technology.

    Quote Originally Posted by MattybPDX
    If my jeep is going to be a grocery getter it's at least going to be a friggin awesome one.

  4. #4
    prerunner1982's Avatar
    prerunner1982 is offline Level: Uber Jeep Cherokee Trailer Queen
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    Default Re: 1998 XJ 4.0L 02 Sensor question

    Jared,

    Welcome to XJTalk. As Tony said the one closest to the engine, commonly referred to as Sensor 1 has more impact on the fuel metering. Sensor 2, further down in the exhaust system after the catalytic converter is an emissions sensor.

    Better MPGs: Done a tune up recently? How about air filter? What was the MPG before the bad O2 sensor?
    1993 2 door 4x4 4.0 5 speed
    1997 4 door 4x2 4.0 auto RIP 6/6/2016
    2000 4 door 4x2 4.0 auto


    Day of Dirt Adventure

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