420 code and then a p0171 on a 2003 wrx sport wagon with 130,000 miles
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This is a discussion on 420 code and then a p0171 on a 2003 wrx sport wagon with 130,000 miles within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; hi, my wrx sport wagon was showing a 420 code so i took it in to the shop figuring they ...

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    420 code and then a p0171 on a 2003 wrx sport wagon with 130,000 miles

    hi,

    my wrx sport wagon was showing a 420 code so i took it in to the shop figuring they would replace the cad. converter. right before i took it in some gaskets blue and the car sounded like it didn't have a muffler. when i took it in they replaced the o2 sensor and the gaskets and then stated that while they weren't sure if it would be fixed the check engine light did turn off. it came back on shortly after i got it back from them. this time it showed a p0171 code. they told me that it could be anything from vac. tubes to simply reseting the computer at the dealership. i find it odd that the 420 code had now been replaced by a p0171 code which seems like it could signficantly more complex. any ideas on what happened? im not very educated on these things so any help would be appreciated.

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    Quote Originally Posted by timmyflash View Post
    hi,

    my wrx sport wagon was showing a 420 code so i took it in to the shop figuring they would replace the cad. converter. right before i took it in some gaskets blue and the car sounded like it didn't have a muffler. when i took it in they replaced the o2 sensor and the gaskets and then stated that while they weren't sure if it would be fixed the check engine light did turn off. it came back on shortly after i got it back from them. this time it showed a p0171 code. they told me that it could be anything from vac. tubes
    A vacuum tube is a thermionic valve. They probably meant a vacuum hose. They could be right.

    to simply reseting the computer at the dealership.
    There is no need for a dealer to reset the ECU. Anyone can do this by removing the battery negative terminal and stepping on the brake pedal for a few moments.

    i find it odd that the 420 code had now been replaced by a p0171 code which seems like it could signficantly more complex. any ideas on what happened?
    They may have left something disconnected.

    You may have a vacuum leak.

    You may have a boost leak.

    You may have a dirty MAF sensor.

    You may have a dirty air filter.

    You may have a combination of the above.

    All this assumes your car is stock.
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    i had the 2 cads replaced, fuel filter and air filter replaced. still getting terrible gas mileage and the check engine light has come back on. will have to see if there is something disconnected with the vacuum leaks.

    Quote Originally Posted by SD_GR View Post
    A vacuum tube is a thermionic valve. They probably meant a vacuum hose. They could be right.



    There is no need for a dealer to reset the ECU. Anyone can do this by removing the battery negative terminal and stepping on the brake pedal for a few moments.



    They may have left something disconnected.

    You may have a vacuum leak.

    You may have a boost leak.

    You may have a dirty MAF sensor.

    You may have a dirty air filter.

    You may have a combination of the above.

    All this assumes your car is stock.

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    Both codes are related to the O2 sensor output. Either your O2 sensor went bad (again) or you may have an intake or exhaust leak. MAF sensor may also be responsible.
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