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Thread: More Issues P0491 and P0492 codes

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    More Issues P0491 and P0492 codes

    So CEL came on this afternoon, scanned codes and P0491 an 492 showed up.
    Reset stayed off for a bit but popped up again, any one know the severity, diy and
    costs?

  2. #2
    Registered User ttboost's Avatar
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    Quote Originally Posted by cruzanrs6 View Post
    So CEL came on this afternoon, scanned codes and P0491 an 492 showed up.
    Reset stayed off for a bit but popped up again, any one know the severity, diy and
    costs?

    Secondary Air for both sides...likely a pump...Do a search here. Do you hear a sound that resembles a 747 landing on your hood? Pump is an easy DIY, in the engine bay, passenger side, bolted to inner fender...couple of bolts, hoses and a plug...have your tuner code it out, remove pump, remove combi valves and buy the plates for the heads...

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    So pump is not really necessary ?

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    Registered User ttboost's Avatar
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    No. It's an emissions thing...when you start the car, it pumps fresh air into the exhaust to create a lean condition for about a minute or so, as the ECU is creating a rich condition for cold starting. Many here delete the hard parts and have their tuner code it out. Search "secondary Air" here.

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    Registered User Bigglezworth's Avatar
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    Next to impossible to delete with engine in situ. Diffuclt to get tools to the back of the head where you need to remove small allenhead bolts to remove the Kombi valves. If you need a replacement pump and can't locate one locally, I have a spare here that can be purchased and shipped.
    '02 S6 Avant Silver - Pokey | Carbon Black/Ebony RS6 w/ stuff - darn quick | '03 Daytona Grey/Ebony RS6 w/ more stuff - quicker yet | '91 NSX CDN issue with 6spd & BBSC - quicker yet and then some | '87 Buick GNX OEM clone w/ lots of stuff - quickest hands down

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    To add to Bigglez's comment: I did it with the engine in place, difficult but not impossible. I had to modify an Allen wrench (ground the short end of an "L" shaped wrench even shorter) to get the bolts, but it was absolutely a lot easier than removing the engine... Just to clarify, those bolts (two on each side) are the ones that hold the Kombi valves on. You'll need to replace the valves with block off plates (you can buy them from a few different sources, I can't recall where I bought my offhand), which means you need to reinstall the bolts as well to hold the block off plates on. Other than those four bolts, the rest of the delete is easy. I left the solenoid (near the front of the engine, right on top under the intake box) installed and just connected a short length of vacuum hose to both of the nipples on it, effectively "looping" them together. I never had anyone modify the ecu and still never had any codes after deleting the system.

    Looks like you're local to me (I'm just north of the river), if you need any more information let me know.
    RS6 #1, 01E, 2.5" straight pipes, AMD Stage 1 6MT tune, 460awhp/530awtq on AMD's Mustang dyno. TOTALLED.. RS6 #2, Ebony Black Pearl on black/silver combination with carbon, up and running with 6 gears and AMD tune.

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    Registered User Bigglezworth's Avatar
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    Quote Originally Posted by P1054 View Post
    To add to Bigglez's comment: I did it with the engine in place, difficult but not impossible. I had to modify an Allen wrench (ground the short end of an "L" shaped wrench even shorter) to get the bolts, but it was absolutely a lot easier than removing the engine... Just to clarify, those bolts (two on each side) are the ones that hold the Kombi valves on. You'll need to replace the valves with block off plates (you can buy them from a few different sources, I can't recall where I bought my offhand), which means you need to reinstall the bolts as well to hold the block off plates on.
    Did you remove the valves at the top of the riser tubes or from the back or the head? You indicate two bolts for each which suggest such. The riser on the drivers side has three bolts at the connection to the head which is where it's common to cap.
    '02 S6 Avant Silver - Pokey | Carbon Black/Ebony RS6 w/ stuff - darn quick | '03 Daytona Grey/Ebony RS6 w/ more stuff - quicker yet | '91 NSX CDN issue with 6spd & BBSC - quicker yet and then some | '87 Buick GNX OEM clone w/ lots of stuff - quickest hands down

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    I removed them at the back of the head, and now that you mention it I do seem to recall three bolts on the one side. Thanks for pointing that out, could definitely help someone trying to do it!

    https://store.034motorsport.com/sai-...ve-40v-v8.html
    Link to the block off plates I used. Could probably make your own pretty easily with a milling machine if you have access to one.
    Last edited by P1054; December 30th, 2016 at 07:19. Reason: Added link
    RS6 #1, 01E, 2.5" straight pipes, AMD Stage 1 6MT tune, 460awhp/530awtq on AMD's Mustang dyno. TOTALLED.. RS6 #2, Ebony Black Pearl on black/silver combination with carbon, up and running with 6 gears and AMD tune.

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    Registered User hahnmgh63's Avatar
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    I also have a SAI pump removed 3 or 4 yrs ago and close as far as shipping goes, close to Mt Rainier. I also used the 034 plates.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

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    Registered User Aronis's Avatar
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    you guys with your lax auto emission inspection laws.....if I did that in NY state they would probably impound the car and hang me...

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  11. #11
    Registered User mgmarsh39's Avatar
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    Just had mine tuned out of the car. Was throwing similar codes.

  12. #12
    Registered User Aronis's Avatar
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    when you tune it out, does the emissions inspection show a problem? or does it fool them?

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

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    If you want to get a good view of the parts you need to remove, feel free to come by and see mine while the engine is out. I am also planning to remove and block off the whole setup, which means I also have a spare pump

  14. #14
    Registered User hahnmgh63's Avatar
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    Good question Mike. Part of WA state here does emissions but I don't have to in my area. I don't have a CEL with the SAI coded out but some have said that with the Eurocharged tune it won't pass a readiness test. Probably will vary what each state requires. I'm going to be re-flashed (hopefully tuned on the dyno) by AMD so I will ask them about that when I get it tuned.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

  15. #15
    Registered User mgmarsh39's Avatar
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    Quote Originally Posted by Aronis View Post
    when you tune it out, does the emissions inspection show a problem? or does it fool them?

    Mike
    TX only checks the obdii port so it fools the system.

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