Question about 2001 Audi TT

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Check engine light

Have a 2002 Audi TT quattro--owned since new--44K miles---check engine light periodically comes on---dealer replaced the temp guage sensor---said it was fixed. After 50 miles, check engine light came on again---took it back--- dealer now says "fault 44936 - seconary air flow too low---checked secondary air pump, vacuum solenoid and combi valve, etc....can't find anything wrong. Now recommends pulling the cylinder heads and checking for carbon buildup in the intake manifolds??? $ 2000 -- and no guarantee that is the problem. Doesn't sound right to me. Any ideas?

Posted by mduffymd on

  • mduffymd Jun 06, 2009

    Guru -- thanks. Took it to AutoZone (very helpful guys but clueless about Audi's). The fault code is P0411

    The air injection system is monitored for faults. Probable cause:

    1. Faulty Air solenoid valve
    2. Faulty air pump motor
    Sounds like the dealer checked on some of these and couldn't find a problem.
    What is your take on this? Thanks very much.



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Funny that they changed the temp guage sensor....known problem on pre-2001 Audi TT and VW engines. Maybe yours was an early build 2002, so they helped you avoid a future problem.
As for the air flow, another known problem is the MAF (mass airflow) sensor. Don't panic, as this is a do it yourself job. Very likely problem if you ever installed a K&N type aftermarket air filter. These oiled filters cause buildup on the sensor. Free fix is to take the sensor body off (its the big ring/pipe coming off the air filter box before the rubber air intake hose) and clean the senor with isopropyl alcohol. Sensor body comes off by loosening the hose clamp on one end, and two screws into the filter box on the other. Don't forget to release the wiring harness plug by gently releasing the tab with a flat head screwdriver.
If your not comfortable with the cleaning, just find the MAF part on-line...about $200 bucks for a new one from Bosch. Very easy to do it yourself and a common failure point on the Audi.
For those still having the coolant sensor problem, also easy to replace yourself....about $10 bucks with a new o-ring.
Like GURU said, a code reader tool will tell if you have these problems, after the engine light comes on.

Posted on Jul 03, 2009


Jeremy Dellow

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Nope, no reason to tear that down, and if there was buildup in the intake manifold, that comes off BEFORE the heads. Go to AutoZone or Advance Auto Parts, have them scan the car for codes, get the codes, and post them here as a reply. I can define the codes for you and point you in the right direction. The form of the code will be P0xxx, where xxx is a number. I have a list of the codes and can help you out once I see them.

Posted on Jun 01, 2009

  • Jeremy Dellow
    Jeremy Dellow Nov 08, 2009

    OK, the P0411 is indeed the Secondary Air Injection System (sometimes, although they get the P code correct, their definitions aren't always right). Failure of this is somewhat common. The secondary air pump (SAP) is used on cold start to help with emissions. When you start your car, it idles at about 1300 RPM at first, and after 30-40 seconds you'll notice the revs drop and the car gets quieter. The SAP is running for that first period of time.

    When you cold-start the car, do you hear a whining noise, like a shop-vac, which goes away after the first minute or less? If so, the SAP itself is failing and must be replaced. If not, it could be a solenoid, or you may just have a vacuum line that has become disconnected. Check the engine bay for any vacuum lines that aren't connected. In my 99 A4, the SAP is in the lower passenger front corner of the engine bay behind the foglight. In the TT, I believe it's also mounted down low, but it may be on the driver's side. The best place for the best info on fixing a TT SAP problem is (free registration - just sign up, check the search feature out to see if you can find the info, and if not, post in the TT section of the forum). I'm a site moderator there and I can vouch for the knowledge of the TT guys on board - they really know this car inside and out.




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.code po411 secondary ari injection incorrect upstream flow detected. will driving the car with this problem cause any damage?

Posted on Nov 19, 2009

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