Secondayr Air Injection System! Let's all learn WTF it does! And HOW!?!?!

[Aronis]

Hello all,

I have posted a few questions about this before and have been learning.

I now get a code for each side and I am fairly sure the Pump is still working.

My questions arise from an Engineering background.

I have pulled up the Wire diagrams and Schematics from the eBahn Bentley Manual as well as grabing a diagram from the Audi dealer for parts.

The first time the CEL went on for the 17819 - Secondary Air Injection System: Bank 2: Insufficient Flow, P1411 error message, I had just had a temp sensor changed (Sensor -1- for exhaust temperature -G235 I believe) under warrantee. After that repair the CEL came on. So I just LOOKED and found the vacuum hose torn off the Mechanical combination valve for secondary air system. I fixed that and the CEL never came on again. This was in June 2009.

So I recently changed the spark plugs (4/10) and a week later the CEL was on for code 17831 Bank 1!

I ordered new vacuum hoses suspecting that a hose is leaking from that side.

So WTF am I getting at?

I looked at the diagrams and I'd really like to know how the system knows that there is a small leak from a VACUUM HOSE one once side that is about 18 inches from the OTHER BANKs Combi Valve?

I understand that the Combi Valve is OPENED by the vacuum and thus the Secondary Air pump can pump air through the exhaust manifold but how does it sense this leak and more importantly how does it sense which side?

From this I have to try to figure out if the leak is truly the vacuum line or is it on the other side of the Combi valve?

From what I can see the Pump has two wires: Ground and Plus 12, no sensor.

So what can you tell me?

I priced the Secondary Air pump ($729.75) and the Combi Valves ($215.25 and $225.75? price different for each side WTF). I am sure this is covered under my extended warrantee, but that is only if they actually FAIL...as long as it's just a Intermittent problem, I have read online they will not cover changing the pump or Combi valves! I think those are ok, hard to believe the pump would intermitently not work without any loud bearing noise or something.

Mike

[terrytcl]

my suspect is that vacuum of the system is measured by the map sensor.

if there's a leak, the map sensor will detect a lack of vacuum in the system / engine.

that's my guess.

or.... you can get a software upgrade that eliminates your air pump system. i know of a couple of tuning places that'll do this for you. that and the secondary o2 sensors.

basically, eliminate the obd2 system of your rs6 with exception to the purge system.

[V8weight]

When the SAP fails, it's usually easily visible. They actually separate at the seams. I would assume if it looks to be intact and you hear it running upon cold start-up you're fine there. I would assume that the secondary air flow would be measured by the primary O2 sensors? It only makes sense to me as the whole point of the system is to warm up the catalysts and there are no other sensors or monitors in place to measure the SAP flow. I'm going to have to go out and take a better look at my car, but if it's not a broken vacuum line you're dealing with, I would say you have cracks in the larger rubber hoses that connect the steel SAI lines on they're way to the exhaust. I had to replace all of these on my Passat 1.8t due to the same SAI insufficient flow codes.

[V8weight]

Edit: I guess it makes more sense to think that maybe the SAI flow would be measured via the secondary O2 sensors as they are post catalyst.

[skribe]

FWIW, I had a SAP whine on cold start on my 1.8t... The unit was malfunctioning and triggered a CEL. The rivets that hold the casing together were failing (common failure on many VAG SAP units.) Before dropping $275 on a new one I drilled out and replaced all the pop rivets... which fixed it for nothing.

Of course on that car the SAP was quite easy to get at, in contrast the the 10 pounds of stuff in a 5 pound sack that is the RS6 engine room.

[V8weight]

FWIW, I had a SAP whine on cold start on my 1.8t... The unit was malfunctioning and triggered a CEL. The rivets that hold the casing together were failing (common failure on many VAG SAP units.) Before dropping $275 on a new one I drilled out and replaced all the pop rivets... which fixed it for nothing.

Of course on that car the SAP was quite easy to get at, in contrast the the 10 pounds of stuff in a 5 pound sack that is the RS6 engine room.
You are 100% correct about the rivet failure at the seams, that's what I was getting at. The SAI pump is actually right out in the open on our cars, it's that gigantic eyesore on the passenger side of the engine bay.

[Aronis]

Thanks all.

Measuring at the 02 sensor makes some sense. So it would be looking for high O2 as the pump is pumping 21% oxygen to mix with exhaust (low O2 after burn). But the system must do something to compensate for the higher O2 during the warm up period.

I'm still looking for more info. This would be a similar system in most cars??

Thanks,

Mike

[V8weight]

Mike, shoot me a PM with your email address, I have the Bosch Mototronic OBD system strategy pdf. Page 22 details the SAI, it should give your mathematical mind something to chew on for awhile :)

[V8weight]

Nevermind, I forgot I could just host it. Take a look through this:
http://dc244.4shared.com/img/274662370/ba8e5334/Bosch_Motronic_ME7_OBD_System_.pdf (http://www.4shared.com/document/wy1KJrZu/Bosch_Motronic_ME7_OBD_System_.html)

[Aronis]

bingo, it's is the oxygen sensor which is the key monitoring input, so that does not yet solve the question as to how it determines a 'small leak detected' as opposed to no air being injected at all. More reading...

great help V8weight, that's a nice article (100 pages, chuck full of learning material) thanks 1,000,000.

Mike

[Aronis]

well the best I can determine is that a vacuum hose leak which is causing the Combi valve to not open fully results in less air being pumped into the exhaust manifold than is expected by the ECU, this must trigger the error message. I did not find an error code in the Bentley manual that said anything more than "Small Leak", so I assume that if there was a lack of actuation of the Combi valve then the error code would be another code such as Failure. I'll have to check later.

Mike

[V8weight]

well the best I can determine is that a vacuum hose leak which is causing the Combi valve to not open fully results in less air being pumped into the exhaust manifold than is expected by the ECU, this must trigger the error message. I did not find an error code in the Bentley manual that said anything more than "Small Leak", so I assume that if there was a lack of actuation of the Combi valve then the error code would be another code such as Failure. I'll have to check later.

Mike
Like I said ealier, there are sections of rubber hose between the combination valves and the steel lines that lead to the exhaust. Be on the lookout for cracks in those hoses as this will cause a low flow condition as well. Good luck:)

[Aronis]

yes, I have the part's numbers for those hoses....thank you!

Mike

[ben916]

This forum just keeps getting better and better with all this information and EXPERTS!

[Aronis]

Finished the replumbing of my emission system today. The tubing was torn on both sides at the connection to the Combi Valves.

Photo's to follow...

[Aronis]

9791 This is the Bank 2 side (driver's side) with prior repair 2 yellow zip ties

9794 Engine

9793 This is Bank 1, tube completely separated! "Small Leak?"

9790 The same, Bank 1, I probably pulled it off the rest of the way while looking at the middle section..should have looked here first.

9795 Bank 2 after repair.

9792 Connection to the solenoid valve and main vacuum source.

9789 Bank 1 after repair

9788 This connector was different, I could not simply slide the connector off, so I found that the nipple was long enough after cutting the tubing to allow a connection without removing the old tube completely. Any Special Tool to remove those factory clamps???

9796 This is the vacuum tube going to the vacuum reservoir. All the rest of the vacuum lines need to be replaced. Many are accessible without removing the air filter housing.

[Aronis]

Yes I used Zip Ties. There are many there, some are brittle and break easily, but that's what I had available. The Tubing (silicone) does snuggle fit on the nipples, but I think the zip tie is needed just the same.

The main leak points I feel were right at the nipple on the Combi valve. Any pulling while manipulating the Air Cleaner box pulls on these two points the most. The rest of the tubing was in rough shape, but I did not fine any other clearly leaking points.

I was going to pressurize with a syringe and adapter (grabbed one from work) but I did not need to since the leaking point was so obvious.

Let see if the CEL stays off for a while!

Mike

[SteveKen]

I've been told that all this stuff can be removed. I'm guessing it would require some major tuning as a result.

[Shoppinit]

If you cut out the SAI system, don't you risk poisoning your cats?

[Mikk23]

Ok...so I'm having SAI issues as well...its throwing codes P0491 and P0492. The pump itself runs fine and has no apparent separation at the seams or rivets. When I got the car the CEL was on...I cleared it and the codes come back after a cold start, but the CEL remains off. I'm guessing after a few iterations of this insufficient flow it will kick the light back on. So I thought I would follow suite and check all the vacuum lines. Heres a few pics:

Drivers side
http://i559.photobucket.com/albums/ss35/mikk23/vac1.jpg

http://i559.photobucket.com/albums/ss35/mikk23/vac2.jpg

http://i559.photobucket.com/albums/ss35/mikk23/vac3.jpg

All the lines look just about brand new...should I replace them anyway? Could it be as simple as the combi valve (by the way...is that it in the last pic)? Any input would be great. Thanks!

[Aronis]

That last picture is the Solenoid Valve.

Gently pull on the tubing at the Combi Valve (your first picture), it the tubing is "Good" is should handle a good pull, otherwise you can pressure test it.

Disconnect and apply pressure with a 10 cc syringe (get a good seal) and if it holds pressure its good.

Mine was very obviously bad.

The same error code can point to the Combi valve, but they are easy to test, the process involves applying vacuum to the vacuum nipple while blowing in the bigger tube, if blows easily valve is working.

Mike

[Mikk23]

Ok...so let me know if I'm understanding correctly. I pulled on the tubing earlier today and everything was snug. But to check the combi valve...I disconnect the vacuum line and use a syringe to blow air into the valve and it should hold the pressure. And by applying vacuum to the same spot I should be able to blow air into the big tube that comes out the otherside freely. So you test the combi valve in these two ways...am I on the right track? Is there a way to test the solenoid valves or do they rarely fail? Thanks for your help!

[Aronis]

Not sure if you can apply enough vacuum with a syringe to actuate the Combi valve.

on the outflow side of the solenoid you will find a vacuum if you disconnect (even with car off due to vacuum reserve). So you can disconnect the inflow tubing and actuate the solenoid with 12 volts, you;ll hear and feel vacuum if the valve opens. (briefly since the reserve is about 5 seconds if I recall).

[V8weight]

You docs and your syringes, these things are like $30 and you can use them to test every vacuum component on your car.
http://www.mityvac.com/pages/products_hvpo.asp

[Mikk23]

Ok fellas...I spent 4 hours with my laptop in bits and pieces trying to get it to work again so I could get a real scan done with my vagcom...lucky me with the help of a youtube video on how to use a heat gun to reflow the soder on the on board video chip and a penny as a better thermal conductor to keep it from debonding itself again, I'm back in business (damn you HP). I checked the vacuum lines the best I could when I had the airbox off...I haven't disconnected any of them to actually check "vacuum" yet but plan on it. So the question is if this might provide some insight to some of you rs6 pros to what my issue may be, and...which of these codes is putting my car in limp mode? Doesn't seem like any of them should but then again I'm a noob. Heres the faults I got:

Address 01: Engine Labels: 077-907-558-BCY.lbl
Part No: 4D1 907 558 D
Component: 4.2l V8/5VT G 0003
Coding: 0006752
Shop #: WSC 02561 772 34112

4 Faults Found:
17831 - Secondary Air Injection System; Bank 1: Insufficient Flow
P1423 - 002 - Lower Limit Exceeded - MIL ON
17819 - Secondary Air Injection System; Bank 2: Insufficient Flow
P1411 - 002 - Lower Limit Exceeded - MIL ON
16815 - Warm Up Catalyst; Bank 2: Efficiency Below Threshold
P0431 - 001 - Upper Limit Exceeded - Intermittent
16805 - Warm Up Catalyst; Bank 1: Efficiency Below Threshold
P0421 - 001 - Upper Limit Exceeded - Intermittent
Readiness: 0000 0000

Address 03: ABS Brakes Labels: 4B0-614-517.lbl
Part No: 4B0 614 517 AD
Component: ESP 5.7 RS 6 2310
Coding: 06697
Shop #: WSC 00000

2 Faults Found:
01119 - Gear Recognition Signal
35-10 - - - Intermittent
00526 - Brake Light Switch-F
27-10 - Implausible Signal - Intermittent

Address 08: Auto HVAC Labels: Redir Fail!
Part No: 4B0 820 043 AM
Component: A6-Klimavollautomat 0105
Coding: 00010
Shop #: WSC 00000

1 Fault Found:
00716 - Air recirculation Flap Positioning Motor (V113)
41-10 - Blocked or No Voltage - Intermittent

[V8weight]

A: You need a new brakelight switch, this is what's cutting boost, not the SAI.
B: The SAI is still going to need to be troubleshot to determine the cause of the problem. You'll have to pull vacuum on the combination valves to see
that they not only actuate, but hold vacuum and stay open. If so then you have to power the vacuum solinoid to see that it is switching vacuum to the combination valves, assuming that the pump itself is operational.
C: You'll have to remove your glovebox assy, and hvac blower motor and have a look inside the plenum for debris or corrosion around the flapper. If all looks clean you'll have to power the actuator motor to see if the flap moves or not. I'm putting my mony on a blockage due to debris. Hope this helps.

[skribe]

What he said.

[Shoppinit]

Weird that there's no DTC in the tranny module with a brakelight switch problem.

[Mikk23]

Brake light switch is the root of my problems eh...well safety first says the RS6. I once more got to experience the full RS6 today...and wow. This time it came out of limp mode under acceleration at about 20mph and held it all the way to 80 (had to let up for fear of jail). This car is amazing when its on its game so to speak. Is this troublesome switch located up in front of the brake pedal?

[V8weight]

I did a write up on how to access the brake light switch on the 2nd page of this thread.
http://www.rs6.com/showthread.php/18574-Traction-control-light-goes-on-around-80-100mph-acceleration.../page2?highlight=p3u+boost+esp

[Mikk23]

Awesome...thanks guys...I'll give this a shot and then tackle the SAI issue.

[Mikk23]

Ok...still waiting on the flapper and brake light switch...but I did do some SAI troubleshooting today. Pulled the vacuum line that goes from the solenoid valve to the reservoir off and checked for vacuum...gave me a good five second hiss. I made sure the solenoid valve itself was closed without power...then put power to it with the Vagcom and felt it click (in hindsight I should have tried to blow into it to see if it was actually opening...oh well). Then I put vacuum to the line that runs out the solenoid valve to the combo valves and it held it just fine. After that I pulled the hose off of the SAI pump itself and blew into it...not very tasty. But no air is leaking by the combo valves...then I again applied vacuum to the lines coming off the solenoid and blew into the hose aaand.....I could blow in there...but I had to blow fairly hard and the passenger side combo valve literally sounded like a duck call. I'm assuming thats a bad thing as the driver side valve was silent. So since my fault code says insufficient flow...if the combo valve isnt opening all the way...might I have found the issue? It threw the code for both sides though but only that passenger side one made the duck noise. I must have looked like a fool doing this whole procedure lol.

[ben916]

Ok...still waiting on the flapper and brake light switch...but I did do some SAI troubleshooting today. Pulled the vacuum line that goes from the solenoid valve to the reservoir off and checked for vacuum...gave me a good five second hiss. I made sure the solenoid valve itself was closed without power...then put power to it with the Vagcom and felt it click (in hindsight I should have tried to blow into it to see if it was actually opening...oh well). Then I put vacuum to the line that runs out the solenoid valve to the combo valves and it held it just fine. After that I pulled the hose off of the SAI pump itself and blew into it...not very tasty. But no air is leaking by the combo valves...then I again applied vacuum to the lines coming off the solenoid and blew into the hose aaand.....I could blow in there...but I had to blow fairly hard and the passenger side combo valve literally sounded like a duck call. I'm assuming thats a bad thing as the driver side valve was silent. So since my fault code says insufficient flow...if the combo valve isnt opening all the way...might I have found the issue? It threw the code for both sides though but only that passenger side one made the duck noise. I must have looked like a fool doing this whole procedure lol.

Man you are are creative!
But I woulda laughed my a$$ off to see/hear that!

[Mikk23]

Ask and you shall receive my friend...make fun of me all you want lol...credit goes to my wife. I wanted to get your opinions on the sound anyway. After I shot this video I took this one step further however...it struck me that my car had been sitting for the entire afternoon and was stone cold. So I again disconnected the hose that went to the SAI pump and reconnected the solenoid vacuum lines...and cranked the beast up. Sure enough on comes the SAI pump...I was able to put my hand down and feel it put out plenty of air. Now correct me if I'm wrong...but at this point the solenoid valve should receive power and open while the pump is operating, yes? After I felt the air coming out of the pump to my satisfaction I again blew into the hose...and nothing (except going red in the face). The combo valves were closed. I then quickly disconnected the vacuum line leading out of the solenoid heading to the combo valves and felt the nipple at the solenoid...no vacuum. I then pulled the line from the solenoid that heads to the reservoir...plenty of vacuum. So vacuum is going in, but its not switching to open up the combo valves...hence insufficient flow...or no flow. Anyway...maybe the combo valves are fine but I just don't have enough hot air in me to open them up like the SAI pump does and they were fluttering making that goofy noise? Is my solenoid valve diagnosis correct? Thanks again!

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[V8weight]

It sounds like you've got it. To be definitive you could connect a vacuum gauge to the combination valve side of the switch, then trigger the switch with the vag see if it's actuating.

[Mikk23]

Alright RS6 experts...riddle me this one. I've narrowed it down to this: The car isn't telling (sending voltage) to the solenoid valve and because of this...obviously...the combo valves remain closed. I put 12 volts to my solenoid valve and tested it and it does in fact work just fine. So why on earth would the car tell the SAI pump to kick on...and not the solenoid valve? They should come on at the same time for everything to work. I tested the connector for continuity and everything looks fine...its connected to something at the other end at least. Further more when I hooked up the VAG I was able to run the engine output tests and feel the thing click open and closed. This just makes no sense...

[snoopra]

Is there a solenoid, in the fuse box(s) that sends the actuating signal for the solenoid valve?

[Mikk23]

shoot I dont know...anyone have a wiring diagram that could answer that question? What tells the Solenoid valve to open?

[Aronis]

Well, I used what was handy!


You docs and your syringes, these things are like $30 and you can use them to test every vacuum component on your car.
http://www.mityvac.com/pages/products_hvpo.asp

[V8weight]

Well, I used what was handy!
No offense intended Mike :) I'm just saying that with the Mighty Vac, coupled with the gauge, you can pull vacuum on components, then watch for a drop in vacuum to diagnose component failures. For a $30 tool, I would say it is a must have tool for any DIY'er.