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    Thread: Emissions Agent on Power Trip and Intermittent Secondary Air

    1. Member
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      May 18th, 2013
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      2004 Phaeton V8
      08-01-2020 07:09 PM #1
      Trying to diagnose the following codes:

      They are intermittent. I could drive for a week or more and have no error codes or I could drive for one day and they pop back up.

      17819 - Secondary Air Injection System: Bank 2
      P1411 - 002 Insufficient Flow

      17831 - Secondary Air Injection System: Bank 1
      P1423 - 002 Insufficient Flow

      I'm thinking it is likely the blower motor or electrical. I tested the blower with a separate battery and it powers up. Could there be a bad spot on the motor commutator? Several years ago I replaced one of the combi valves and it was a pain.


      This has been frustrating to say the least. My 2004 Phaeton should pass the emissions test per the state standard, but the ladies and men at the testing center aren't having it. The first time I showed, no codes, all readiness monitors state "pass", I fail. Reason - My OBD port was hanging from the dash because I had the trim piece out. They refused to test it because "they might break it". I offer to plug it in, they say no. Of course instead of telling me this and letting me go on my way, they enter a fail in the system. You only have so many fails, and honestly I don't know what happens if I have to many. Today, before I go, all the readiness monitors say "pass" but I have a check engine light on and I know I have error codes on the engine module. I didn't want to clear the codes because I know it can take days to get everything back into readiness and I risk going back to a fail on the readiness. My understanding is you can have one "fail" on the readiness to pass.

      So I drive up to the testing center and ask before any testing is done: Will fail if you have error codes or a check engine light. I state that it is my understanding they only check readiness and you can have one system down. The attendant confirms my understand and says the check engine light and error codes don't matter. I'm happy because I know it will pass based on this confirmation. The attendant gives me the print out and says I failed because I have a check engine light on and have error codes that I need to get fixed. WTF! He just said the opposite. So, now I have two strikes. If these people were being honest they should of told me to come back later after I had the things fixed.

      So anyway, I still want to fix the secondary air as long as it's not a crazy job. I can do the work myself but I know accessing any of the plumbing is very difficult. When I changed the Combi valve I was able to avoid removing the valve cover, but it was a total Bi***. I took all day because there was no access.

      Suggestions on a fix? An envelope stuffed with cash handed to the attendant, a pie, sweet talking, or actually fixing the problem. I would try and clear the codes, but at this point I have enough strikes against me that that could backfire and I really don't want to see that little light on the dash anyway.

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    3. 08-02-2020 01:33 PM #2
      Check your vacuum lines first. Did you change all the vacuum lines when you changed the combi valve? I replaced all mine with high-temperature 3D printer PTFE tubing, which seems to be holding up well. Assuming it's not the lines (I'd put good money down that it is), the pump isn't too difficult to get to, it sits at the front left corner, right down at the bottom.

    4. Member
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      2004 Phaeton V8
      08-02-2020 03:16 PM #3
      Would vacuum lines be intermittent? I guess that depends if the secondary air turns on at every start up? I recall it being operational at certain temperatures. I did partially replace the vacuum line prior has the hose was cracked. I replaced the missing section. I know where the pump sits, but not how to remove it. Is there an easy way. How about the solenoid?

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    6. Member
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      Feb 10th, 2015
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      08-02-2020 05:40 PM #4
      In UT, a CEL will cause an automatic fail. You can have one readiness monitor fail.

      I agree with Martin.

      I also agree with you about the solenoids.

      Check the vacuum lines. While you are there, check the solenoids.

      The VW Master Mechanic at my dealer told me to check all vacuum lines on the engine because any vacuum leak will cause the Secondary Air to fail and turn on the CEL.

      The vacuum lines on my 20014 W12, 8486, snapped like twigs when I was trying to check the system with my vacuum gauge. I could get a pliers down to remove the soft connecting hose on my left Combi Valve but I couldn't even get my hand down in there to replace it. Since I couldn't test my Combi valves, I decided to replace them.

      On the W12 there is another vacuum line that goes to a vacuum solenoid that goes to the engine mounts. It's on the bottom left. That one was broken. That was probably the reason the Secondary Air failed but I broke it good by snapping the vacuum lines trying to test the Combi valves.

      I couldn't get to anything on the front of the engine. The mechanic was able to replace both Combi valves and hook up the vacuum lines without removing the front end. The first day he showed me the busted vacuum solenoid. I bought an OE one with the VW marks ground off and he replaced it for me when I brought it in. I think the labor to replace the vacuum solenoid was included in the original job.

      Good luck.

      -Eric

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      08-02-2020 05:54 PM #5
      Quote Originally Posted by Phaeton2 View Post
      Would vacuum lines be intermittent?
      No, but they might only appear intermittent.

      I don't know how the whole emissions system works, but on 7579 my CEL would come on some times. It had a fault for the EVAP system (Leak Detection Pump). I bought a new LDP but the CEL and fault soon returned. The LDP is a monitoring device for the EVAP system that comes on to check for leaks.

      I was talking to the same mechanic and telling him I could reset my faults and clear the CEL but it would return seemingly randomly. He told me the car checks the emissions system between 1/2 tank and 1/4 tank. Then I noticed he was right. If I kept the tank above 3/4 full, the CEL stayed off.

      I don't know if that's just for the EVAP system or for the entire emissions system but could be an explanation for intermittent failing.

      The LDP problem on 7579 took about $2K to fix. The vacuum lines from the engine to the LDP were torn off in an accident probably before I bought the car.

      -Eric

    8. Member
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      2004 Phaeton V8
      08-02-2020 09:53 PM #6
      sorry, I'm not familiar with some of your abbreviations and want to make sure I am following.

      CEL, 8486, 7579? Where is the Leak Detection Pump?

      Is there a way to force a test with a VAG.COM so I don't have to drive for a week to find if the error pops up? I might try to fill the tank up and see if it returns, might be a way to pass the test if I can't figure it out.

    9. 08-02-2020 10:14 PM #7
      Pretty much any vacuum leak is likely to throw a secondary air CEL. Both comi valves join to a common vacuum connector near the middle of the plenum, and there's a line from there that runs to the variable intake actuators. All those lines probably need to be replaced. Mine literally crumbled in my fingers when I checked them. The pump is underneath and slightly forward of the driver's side airbox. You can hear the pump running when you start the car, it makes more noise if there's a vacuum leak.

    10. Member
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      08-02-2020 11:11 PM #8
      Quote Originally Posted by Phaeton2 View Post
      sorry, I'm not familiar with some of your abbreviations and want to make sure I am following.

      CEL, 8486, 7579? Where is the Leak Detection Pump?

      Is there a way to force a test with a VAG.COM so I don't have to drive for a week to find if the error pops up? I might try to fill the tank up and see if it returns, might be a way to pass the test if I can't figure it out.
      CEL is the Check Engine Light. 7579 and 8486 are the last 4 numbers of my 2004 W12 Phaetons, both of which needed emissions repairs. The Leak Detection Pump is under the spare tire well. It is only a monitoring device for the EVAP system. It actually does nothing to reduce emissions, it only check the EVAP system. It sucks if it breaks because you have to fix it.

      The Leak Detection Pump (LDP) doesn't interact with the Secondary Air Injection System as far as I know. I mentioned it in passing because while my LDP sub-system was broken, the mechanic at the dealer told me that the emissions system checks itself when the fuel tank is between 1/2 and 1/4 full.

      I postulated that that could be why you think the Secondary Air Injection System vacuum hoses could be intermittent. No, they probably can't be intermittent but the symptoms possibly could be.

      I am not well versed in emissions systems. The Phaetons are the only cars that have given me problems but I don't own any other cars with OBD 2. Setting readiness sucks.

      The vacuum lines for the Secondary Air Injection system are extremely brittle. Mine snapped like twigs when I disconnected them to check my Combi valves with a vacuum pump.

      They live in the hottest part of the car, the engine compartment.

      The W12 and V8 have different vacuum hoses. Search the forum for how to replace the V8 Secondary Air vacuum hoses with less expensive, more reliable substitutes. I believe invisiblewave used fish tank hose.

      Any vacuum leak on the engine can affect the Secondary Air Injection System according to the VW mechanic. That can include the Leak Detection Pump (LDP) because it draws vacuum from the engine but VCDS will tell you if the LDP has a fault.

      I also suggested you check the vacuum solenoids because one of mine was broken on 8486 and it was hidden under the car and its other vacuum port goes to the engine mount system. I don't know if the V8 has vacuum controlled motor mounts but I don't know why it wouldn't.

      The vacuum solenoids on the engine were fine.

      I don't know if the following trick works on newer cars, but it worked on older cars to check for vacuum leaks: Spray some starting fluid around the vacuum hoses, vacuum caps and anything attached to the intake and see if the idle changes. Perhaps others can chime in.

      With the V8, I understand you can set readiness with VCDS. Search the forum. It's not a cheat. It's actually in the Bentley manual that the VW mechanics are supposed to set readiness before the car goes back to the customer.

      I don't have a V8 and it doesn't work on either of my W12s. Whoever made the chart for the W12 may have left a step out.

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