change of code
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This is a discussion on change of code within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; if you have an o2 sensor fail and you just clear the code and your engine light comes on again ...

  1. #1
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    change of code

    if you have an o2 sensor fail and you just clear the code and your engine light comes on again for a different fault would the o2 sensor be the one at fault or would it be the new code that came up?

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    Registered User EvoEatr's Avatar
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    It all depends exactly what your talking about..I will say this some damaged sensors/componants can have an effect on other sensors/componants...What codes are/where you getting? What year is your vehicle? how many miles? any recent work performed?

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    the car is an 02 wrx stock except intake but not running a map, the code was for a failed rear o2 sensor and after clearing it it came up with a #4 misfire p0304

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    Registered User EvoEatr's Avatar
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    Ill bet they aren't related...did you end up replacing the rear o2 or just clearing the code? has that specific code come back yet? What was the code exactly P???? It is somewhat rare that rear o2 sensors fail on Subarus..8 out of ten times an o2 fails on these cars its the front one...Is the car actually misfiring? do you feel/ hear/ notice it? When was the last time you changed your plugs? How many miles are on the vehicle?

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    i just cleared it then the code p0304 came up as a misfire but it only seems like it is a little rough when i first start it and i just replaced the front one

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    Registered User EvoEatr's Avatar
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    Quote Originally Posted by EvoEatr View Post
    When was the last time you changed your plugs? How many miles are on the vehicle?

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    i changed the front one right before 69k and its now at 71k

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    Registered User EvoEatr's Avatar
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    You changed one spark plug?..Cylinder 4 is the the drivers side rear cylinder....I recommend pulling the coil/plug out and inspecting them...

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    ok i will get help with that cause im still new to seeing how a subaru engine works, but if i just cleared the code for the rear o2 sensor that wouldn't have an impact on the misfire cause afet i just cleared it i reset the ecu.
    and when the rear one failed the temperature sensor failed too and there was no resistor in the harness so i put one in due to the fault.
    it also says that the most common reason for a misfire is the fuel injector, so i put in some injector cleaner and when i got to half a tank it went away for a day, that why im curious if the rear o2 sensor is still faulted or not.

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    Quote Originally Posted by smugglin1986 View Post
    ok i will get help with that cause im still new to seeing how a subaru engine works, but if i just cleared the code for the rear o2 sensor that wouldn't have an impact on the misfire cause afet i just cleared it i reset the ecu.
    and when the rear one failed the temperature sensor failed too and there was no resistor in the harness so i put one in due to the fault.
    it also says that the most common reason for a misfire is the fuel injector, so i put in some injector cleaner and when i got to half a tank it went away for a day, that why im curious if the rear o2 sensor is still faulted or not.
    Where did you read/hear the most common reason for a miss is a fuel injector...I find this extremely hard to believe...90% of the misfire problems I get are either a bad plug, ignition wire, or coil...Personally I wouldn't be listening to whatever source you got this info from...Not saying that isn't your problem...You could always swap injectors from cylinder 2 to cylinder 4 and see if the misfire follows? However If you only changed one spark plug I would be replacing them all at that mileage as well as swapping the coil from cylinder 2 to cylinder 4 before I started swapping injectors and such....

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    ok i will try but i have never done one before but what about the question i asked bout the o2 sensor and the ecu?

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    Quote Originally Posted by smugglin1986 View Post
    ok i will try but i have never done one before but what about the question i asked bout the o2 sensor and the ecu?
    I'm assuming your referring to the question about clearing the rear o2 code?..I'm going to say NO Its not that likely that a bad rear o2 sensor will throw a misfire code..Youve never done one before? one what? spark plugs on these cars?..If you need a hand I would be happy to walk you through the process...there not to bad to change...now the early EZ30's thats a different story...lol

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    yes i would like that very much i have really only worked on chevy's and carbureators instead of fuel injection, but do you think i should change the rear o2 sensor even though i cleared it a while back?

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