Secondary Injector Low Flow PDF Print E-mail
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Monday, 05 April 2010 06:31

I recently had a check engine light on my Audi S8. I used Vag-Com to check the fault codes which indicated a low flow of the secondary air pump on banks one and two.

In diagnosing this problem I learned that there is a large air pump located in the air box under the air cleaner. This pump blows air into the exhaust manifolds during cold start and some WOT session to aid in emissions. There are two vacuum operated valves, one at each exhaust manifold, that allow the air from the pump to enter the manifolds.

Because I had a problem on both banks I assumed that it was a supply problem and not an issue with the valve on the manifolds. I again loaded up Vag-Com and used the output test functionality to cycle the air pump. Doing this I determined that the pump was in fact working fine and was supplying air. This was a relief as that pump is over $500. I also used the output test to check the control solenoid for the valve supply and found it was also working fine.

I assumed the problem must then be a vacuum line. I traced out the path of the various lines and found that the one supplying the driver side control valve was indeed cracked. I replaced it, cleared the fault code, and all was well.






Last Updated on Monday, 05 April 2010 07:03