jeffkruse

My MIL light was always on because of the two codes. Has been on for about a year no how matter how many times I cleared them. MIL Light has not been on for about two days since I cleared them. I get the same codes without - MIL ON. Just curious if anyone had any ideas why. Thanks

17831 - Secondary Air Injection System; Bank 1
P1423 - 002 - Insufficient Flow - MIL ON
17819 - Secondary Air Injection System; Bank 2
P1411 - 002 - Insufficient Flow - MIL ON



17831 - Secondary Air Injection System; Bank 1
P1423 - 002 - Insufficient Flow
17819 - Secondary Air Injection System; Bank 2
P1411 - 002 - Insufficient Flow

schiu

I have the same issue for a while. I did changed the secondary air pump but the issue not resolve. The dealer quoted a lot of money to change the whole system . If i don't get this done will it eventually damage my car

MP4.2+6.0

Usual answers:

If you see the code on both sides (banks) of 4.2 motor, suspect the air pump. If you see it on only one side, suspect the vacuum hoses to the combi(nation) valves or the combi valve itself. S8's and W12s have a pump for each side, so diagnostic logic a little different there.

You can test the pump function...with VCDS. Spins up audibly when you run the check. Reason #457 to have VCDS with older Audis. You can also try to get at the power connection for it and apply 12V...the old fashioned way.

jeffkruse

I just thought it was strange that for about a year it stated - MIL ON and now still throws codes but without the - MIL ON. And the light is not on. FYI, had the SAI pumped replace about two months ago and it also did not fix my issue. With both sides anyone know where else I could check.

MP4.2+6.0

Look at vacuum as stated, but I would re test pump too. Make sure you don't have either a faulty one or a wiring or fuse issue. You should have a CEL though if it is faulty. Does take two full cold-hot-cold motor cycles for it to turn on. Sometimes when mine had issues it would take a road trip to get it to trigger.

One more idea is look at the air hoses themselves. On my 2000 4.2 they started to get soft at >10 years, and I was starting to see a little of the same on the W12. If there is a hole, or one of the plastic clamps is messed up, more reasons it could be faulty. Biggest picture though, SAI issues are most commonly the vacuum hoses historically.

richard-tx

I am not sure where the sensor is for the air pump but you might want to make sure that the hose at the bottom of the air filter housing is connected. If that hose is disconnected then dirt and other foreign material can enter the pump, damaging it. Removing the forward wheel well liner makes it easy to check.

the_duke

Or just drop the skid plate. Much easier than the wheel well lining.