Cel codes P1127 & P1129
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  1. #1
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    Cel codes P1127 & P1129

    my 99 v6 has these codes. just had temp sensor (dark green) changed out and was hoping rough idle when hot was cured - didn't work. could a vacuum hose cause codes like these or maybe O2 sensors. Thanks

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  3. #2
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    Banks 1 & 2 system too rich.
    This can be caused by a bad MAFS (Mass Airflow Sensor) and/or
    02 Sensors (heated).

    Lookup your DTC's in the info section... here:
    DTC Lookup Table

    Can you get the car scanned for codes (DTC's)?
    AutoZone does this for free as do many chain auto stores.

    When was the last time you had a thorough tune-up performed?

  4. #3
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    could i just clean the mafs or should i replace it. plugs are about 15000 km old. runs fine at cold start then stumbles when hot. thanks

  5. #4
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    Clean the MAF, check the snow screen and air filter.

  6. #5
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    Yes try that. Make sure you use MAF cleaner specifically.
    It's now sold in most auto stores.

    Double check or just start replacing vacuum lines.
    Also double-check your "L" hose as those are defective.

  7. #6
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    the MAF is a very sensitive piece. it keeps a small wire at a set temp. and measures the amount of voltage required to keep it at that temp. to determine the amount of air coming across it. clean with MAF cleaner only! other cleaners are much too harsh.
    a vacuum leak will cause a lean condition...not a rich one.

  8. #7
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    Update

    so it was the mafs in the end. first cleaned it and had cel cleared. this lasted bout 5 kms. ordered new mafs at napa (143 with tax). kept driving and another issue. trans bangs hard into safe mode - gear display goes dark around letters and it seems to be stuck in 3rd gear. install new sensor, air filter and clean screen. seems to be cured. question - will the cel go away on its own. thanks for all the advise. p s - that cel should look like a dollar sign right

  9. #8
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    The cel will go away after 10 or more starts once the problem is solved. The code will remain stored. You can have the code cleared and many auto parts stores.

  10. #9
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    This was the first thread I found and matched my problem exactly, at least the codes did. Suddenly, yesterday on start up, car would idle roughly and P1127 & P1129. My first thoughts were "here we go again" in terms of car being out of it for weeks. Luckily, I cleaned my MAF and that solved the problem. MAF didn't even look dirty at all. I know this as an old thread, but I figure it's worth adding that cleaning the MAF solved the problem for me as well. I was worried about it being the throttle body bypass, which is a PITA to even get to on the V6.

  11. #10
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    1999 V6

    I am having a similar problem.

    P1127 Long Term Fuel Trim mult.,Bank1 System too Rich
    P1129 Long Term Fuel Trim mult.,Bank2 System too Rich
    Pending P1141 Load Calculation Cross Check Range/Performance

    I got these codes one week ago after filling up with Chevron Premium. In the past I had used 76 Premium without any problems, but that station is closed for road construction so I cannot go back to see if I get the codes with their gas.

    I replaced the air filter, cleaned the slush screen, and cleared the codes.

    The car was running smoothly after replacing the filter, but the codes returned tonight after filling up at a different Chevron with Premium (approx. 173 miles after codes were cleared).

    I have now cleaned the MAF with MAF specific cleaner as well to see if that will help. There was a film on the screen in front of the MAF so there may have been build up on the sensor as well.

    Does anyone know if the P1141 is pointing to O2 sensors or the MAF? For bank 1 and 2 to both be rich I am thinking MAF.

    The vacuum lines are replaced with HoseTechniques silicone so they should be good and I am running between 18 and 22 inHg. I do need to check the line to the vacuum gauge still though. I replaced the coolant temp. sensor around 30,000 miles ago, but I may pick up a new one just to be safe.

    Regarding the defective L hose, I thought they were specific to the 1.8T.

    Any help would be greatly appreciated.

  12. #11
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    You can use this site to get info on most codes, enter the code in the search box. 17549/P1141/004417 - Ross-Tech Wiki

  13. #12
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    Thank you Tomvw!

  14. #13
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    An update:

    I replaced the MAF, coolant temp sender, intake air temp sender and PCV system (which I discovered was clogged and had a failed valve), then thermostat (which had failed), radiator fan switch, vacuum line check valve (new one holds 6-8 inHg overnight vs 0 inHg), all the rubber elbows in the PCV/brake booster system plus the check valve and suction jet pump (newest revision), and spark plugs (which needed to be done anyway), then FPR, and lastly the EVAP purge valve.

    These three codes seem to have been caused by a malfunctioning EVAP purge valve on my V6. I checked it for debris when I removed it and saw nothing and I could not blow through it, so my guess is it was intermittently stuck open or was just slow to close so the car never saw a leak in the system.

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