Never Ending Check Light - Secondary Air Injection
06-17-2017, 01:38 PM
#1
AudiWorld Member
Thread Starter
Never Ending Check Light - Secondary Air Injection
So I have officially replaced EVERY component in the secondary air injection system (EGR valves). Over the last 5 years the problem of the check light coming on randomly for SECONDARY AIR INJECTION - INSUFFICIENT FLOW -BANK 1&2 has plagued me. I reset it and continue to try to find the source and nothing changes no matter what I replace.
I've replaced the vacuum lines, the air pump, the air pump inlet and outlet lines, the little electronic vacuum switch (twice), the combi valves and seals, the bolts for the combi valves, the line that runs between the comb valves. EVERYTHING!
The system seems to run fine. Upon startup the air pump (new) winds up and blows air. There is no problem I can find, except the check light comes on.
Now the check light does not come on all the time. Sometimes it will go a few weeks without coming on. Then bam! it always shows back up.
This has led me to a question I'd not thought of before that I could use some help with. What is it that tells the system there is insufficient flow? Could it be that the system is just wrong and something is telling it there is insufficient flow when there isn't? How does the system know there is insufficient flow?
I've thoroughly gone through the system, there is no sensor in the air flow to the combo valves that measures flow. There is nothing at the air pump that measures flow. The air pump only has two wires for power to it. So what measures flow and comes up with a code to throw that the flow is insufficient?
I take great care of my A8 and it runs like a swiss watch, but the big bright yellow engine light staring me in the face drives me mad!
I've replaced the vacuum lines, the air pump, the air pump inlet and outlet lines, the little electronic vacuum switch (twice), the combi valves and seals, the bolts for the combi valves, the line that runs between the comb valves. EVERYTHING!
The system seems to run fine. Upon startup the air pump (new) winds up and blows air. There is no problem I can find, except the check light comes on.
Now the check light does not come on all the time. Sometimes it will go a few weeks without coming on. Then bam! it always shows back up.
This has led me to a question I'd not thought of before that I could use some help with. What is it that tells the system there is insufficient flow? Could it be that the system is just wrong and something is telling it there is insufficient flow when there isn't? How does the system know there is insufficient flow?
I've thoroughly gone through the system, there is no sensor in the air flow to the combo valves that measures flow. There is nothing at the air pump that measures flow. The air pump only has two wires for power to it. So what measures flow and comes up with a code to throw that the flow is insufficient?
I take great care of my A8 and it runs like a swiss watch, but the big bright yellow engine light staring me in the face drives me mad!
06-17-2017, 05:00 PM
#2
AudiWorld Super User
How about the gas cap? The most simple but fixes most of check engine lights. Pressure test it just like having smog check.
Cheers and good luck,
Louis
Cheers and good luck,
Louis
06-17-2017, 06:20 PM
#3
AudiWorld Super User
06-17-2017, 06:50 PM
#4
AudiWorld Super User
...
This has led me to a question I'd not thought of before that I could use some help with. What is it that tells the system there is insufficient flow? Could it be that the system is just wrong and something is telling it there is insufficient flow when there isn't? How does the system know there is insufficient flow?
I've thoroughly gone through the system, there is no sensor in the air flow to the combo valves that measures flow. There is nothing at the air pump that measures flow. The air pump only has two wires for power to it. So what measures flow and comes up with a code to throw that the flow is insufficient?
...
Obviously if O2's are weak you should have codes for those anyway since they (and catalytic converters) get checked and cross checked by the system internal diagnostics.
Attached are a few links. First is from the company that makes the pump and related components--Pierburg brand. At least that is what I found in my W12 when one (of the two) ate water. Second is a theory of operation and description I found in very quick search that may help. From that description it sounds like you should look at O2 readings w/ VCDS. You can spin pump up w/ VCDS too just in case any doubts there. If all still checks out, then you may have the clogged passages problem. You don't say what motor you have (one of the 4.2's?), but it does come up w/ some of them, particularly 3.2 V6 from other posts I have sen on Q5 board. If FSI, might be somewhat more likely. Maybe search on the clogged passages issue, specific to your motor. Last, when all else fails and assuming you dont want to pull manifold or head(s), maybe try some Seafoam, esp. if FSI, perhaps with Italian tune up run following that.
https://cdn.rheinmetall-automotive.c..._sec_air_e.pdf
Secondary Air Injection (SAI) - Karmakanix
Last edited by MP4.2+6.0; 06-17-2017 at 06:53 PM.
06-17-2017, 10:08 PM
#5
AudiWorld Wiseguy
Looking at the various SSP's, it appears to work by monitoring expected O2 levels in the exhaust based on the air mass meter and fuel mix. So if the O2 levels are lower than expected, then there is insufficient secondary air entering the exhaust.
Given you've replaced everything, seems like you might have blocked air passages. So take the combo valves off blow carb cleaner or sea foam into the secondary air passages to clear them out.
Given you've replaced everything, seems like you might have blocked air passages. So take the combo valves off blow carb cleaner or sea foam into the secondary air passages to clear them out.
06-18-2017, 11:54 AM
#6
AudiWorld Member
Thread Starter
That's what I was thinking too, O2 sensor readings tell if it has sufficient flow based on what the expected O2 would be if the SAI is blowing and the cats are heated up to achieve the reduced emissions expected. One of the symptoms that doesn't quite jive is that the check light comes on when I have been driving for a while, like at least 10 miles, usually more. When the light comes on the engine is warm and usually driving on the freeway quite a bit. I cannot recall the code coming up at all on startup of cold engine. The purpose of the SAI is to provide more air into the exhaust to accelerate heat up of the cats when cold. The "Insufficient Flow" code is always coming on with heated conditions, not cold start conditions.
Perhaps it has nothing to do with the SAI system? Could it be that a condition of increased emissions is present that tells the O2 sensors there is too much carbon and the code that gets thrown is "SAI Insufficient Flow?" The code I get always is for both banks, there are 2 codes one for each bank. It is never for only one bank. I have never had a single O2 sensor code pop up. Only the "SAI Bank 1 & 2 Insufficient Flow" codes.
BTW it is a 4.2 2005, shown at the bottom of my picture. Engine Code BFM. Vacuum actuated combi valves in the back supplied with the air pump mounted at the bottom of the passenger side front bumper extension strut. Pump runs fine, always has, and I replaced it anyways at great expense with a new factory one just to rule that out because I ran out of ideas.
As for the carbon build up I've not ruled that out, but find it unlikely. When I replaced the combi valves I took a piece of tie wire and bent up the end to form a small scraping hook. I slid it into the exhaust chamber through the combi valve entry as far as I could, about 6-8 inches, and I scraped as much as I could. I got no residue coming out with the wire. I blew the holes out with compressed air and nothing came out. I reached in with my pinky finger and it came out clean. There was no visible presence of carbon residue. The old combi valves were fine too, they were clean for the most part inside and seemed to function with a vacuum test on the bench. So I think they were working fine even though I replaced them which is a bitch of a job getting at the little bolts behind the engine without loosing them (thus why I replaced the bolts because they get lost). I've spent countless hours searching every recess of my engine with magnets, flashlights, and fingers to find bolts and those gaskets that drop too. Still, not ruling out that there is some carbon blockage somewhere in the exhaust manifold, but wouldn't that cause other problems as well? And how would clean that out without removing the exhaust manifolds which requires removal of the engine?
Over the years, I've read up and researched the forums as much as possible on this issue. I've written other threads. I've found the threads that describe the carbon build up issue as a potential problem and never seen any resolution of that "potential" issue in any thread. There is one where a guy is talking about his brother or friend who is a mechanic and thinks that is the issue and he is going to do more research, but it never gets resolved. I have not found any thread where it was a carbon build up and someone cleaned it out and the issue was resolved to verify that theory was indeed the problem.
Perhaps it has nothing to do with the SAI system? Could it be that a condition of increased emissions is present that tells the O2 sensors there is too much carbon and the code that gets thrown is "SAI Insufficient Flow?" The code I get always is for both banks, there are 2 codes one for each bank. It is never for only one bank. I have never had a single O2 sensor code pop up. Only the "SAI Bank 1 & 2 Insufficient Flow" codes.
BTW it is a 4.2 2005, shown at the bottom of my picture. Engine Code BFM. Vacuum actuated combi valves in the back supplied with the air pump mounted at the bottom of the passenger side front bumper extension strut. Pump runs fine, always has, and I replaced it anyways at great expense with a new factory one just to rule that out because I ran out of ideas.
As for the carbon build up I've not ruled that out, but find it unlikely. When I replaced the combi valves I took a piece of tie wire and bent up the end to form a small scraping hook. I slid it into the exhaust chamber through the combi valve entry as far as I could, about 6-8 inches, and I scraped as much as I could. I got no residue coming out with the wire. I blew the holes out with compressed air and nothing came out. I reached in with my pinky finger and it came out clean. There was no visible presence of carbon residue. The old combi valves were fine too, they were clean for the most part inside and seemed to function with a vacuum test on the bench. So I think they were working fine even though I replaced them which is a bitch of a job getting at the little bolts behind the engine without loosing them (thus why I replaced the bolts because they get lost). I've spent countless hours searching every recess of my engine with magnets, flashlights, and fingers to find bolts and those gaskets that drop too. Still, not ruling out that there is some carbon blockage somewhere in the exhaust manifold, but wouldn't that cause other problems as well? And how would clean that out without removing the exhaust manifolds which requires removal of the engine?
Over the years, I've read up and researched the forums as much as possible on this issue. I've written other threads. I've found the threads that describe the carbon build up issue as a potential problem and never seen any resolution of that "potential" issue in any thread. There is one where a guy is talking about his brother or friend who is a mechanic and thinks that is the issue and he is going to do more research, but it never gets resolved. I have not found any thread where it was a carbon build up and someone cleaned it out and the issue was resolved to verify that theory was indeed the problem.
Last edited by DA8; 06-18-2017 at 12:03 PM.
06-18-2017, 01:16 PM
#7
AudiWorld Super User
I think if you dig into how the readiness codes work on OBDII you may get better info.
First, check the codes with VCDS and see if indeed the code in the 5th digit for SAI is where the issue is. See table at end of this reply for how to interpret.
Next, realize that if the readiness code is showing not ready, car will throw a CEL if it goes two cold hot cold cycles and can't confirm correct function. Some throw CEL right away, but ones like SAI and EVAP get basically two driving cycle cracks at it before it goes CEL.
Then, realize the test it is running is apparently not a cold test like I believe is what you are probably thinking, but rather one run at a certain rpm while you are driving at a fair steady speed. I think what it probably does is cycle the pump and then look at the O2's for a lambda change at a given RPM and mixture. If it does not see it, it concludes flow is no good. I suspect this is why you are seeing the CEL when driving as opposed to at cold start up. That's my experience IIRC when I have had SAI issues. See link to an attached document from Snap On for various older Audis and how to simulate the driving cycles to reset readiness codes. https://www1.snapon.com/Files/Diagno...CodeCharts.pdf It does cover the V8's from D2 era, but not D3 era. Bentley or somewhere else on web might yield you one specific to your motor. But may not matter; the point is I don't think readiness code for SAI is generated at cold start, and if you indeed find a not ready flag for SAI you will at least understand why and how the CEL is showing up.
The above just helps explain diagnostically what is going on w/ system, but doesn't solve your issue. Skimming through your latest reply, as ideas try:
First, check the codes with VCDS and see if indeed the code in the 5th digit for SAI is where the issue is. See table at end of this reply for how to interpret.
Next, realize that if the readiness code is showing not ready, car will throw a CEL if it goes two cold hot cold cycles and can't confirm correct function. Some throw CEL right away, but ones like SAI and EVAP get basically two driving cycle cracks at it before it goes CEL.
Then, realize the test it is running is apparently not a cold test like I believe is what you are probably thinking, but rather one run at a certain rpm while you are driving at a fair steady speed. I think what it probably does is cycle the pump and then look at the O2's for a lambda change at a given RPM and mixture. If it does not see it, it concludes flow is no good. I suspect this is why you are seeing the CEL when driving as opposed to at cold start up. That's my experience IIRC when I have had SAI issues. See link to an attached document from Snap On for various older Audis and how to simulate the driving cycles to reset readiness codes. https://www1.snapon.com/Files/Diagno...CodeCharts.pdf It does cover the V8's from D2 era, but not D3 era. Bentley or somewhere else on web might yield you one specific to your motor. But may not matter; the point is I don't think readiness code for SAI is generated at cold start, and if you indeed find a not ready flag for SAI you will at least understand why and how the CEL is showing up.
The above just helps explain diagnostically what is going on w/ system, but doesn't solve your issue. Skimming through your latest reply, as ideas try:
1. Pressure test your pump, even if changed. If you still have old one, maybe check it too. Check output against specs provided for system in Bentley or otherwise.
2. Recheck air plumbing between pump and the combi valves. I have seen that hose get soft over the years. I think if it leaks before a combi valve--even after wherever the split/tee is after the pump but before the combi valves--it may code to both sides like you are seeing.
3. Look critically at your suction side hose to pump. On my W12 it comes out of the bottom of the driver's side air box--it does that so it can pull air already filtered by main engine air filter. One time when I pulled fender liner I found thay hose was physically kinked and squeezed under my air box from some prior service work. Something like that would starve pump air intake and thus flow even if pump is good.
4. Get pump to cycle with VCDS--or just power it directly w/ 12V jumpers. Have motor running and spray Seafoam into pump intake (not just the engine air stream in general). Like the takeoff fitting at bottom of air box or wherever yours is. Or, use the tube they give you and spray it into pump output somehow on its way to the combi valves. The idea is to get that solvent in there all the way through the combi valves and out to the passages into the exhaust. Afterward, the Italian tune up drive. Clear codes and see if any better.
Finally, yes agreed w/ some of your commentary about the codes showing on both banks and what that may signify. To me that says probably look more at what is common to both banks, which to me says pump and related plumbing.
2. Recheck air plumbing between pump and the combi valves. I have seen that hose get soft over the years. I think if it leaks before a combi valve--even after wherever the split/tee is after the pump but before the combi valves--it may code to both sides like you are seeing.
3. Look critically at your suction side hose to pump. On my W12 it comes out of the bottom of the driver's side air box--it does that so it can pull air already filtered by main engine air filter. One time when I pulled fender liner I found thay hose was physically kinked and squeezed under my air box from some prior service work. Something like that would starve pump air intake and thus flow even if pump is good.
4. Get pump to cycle with VCDS--or just power it directly w/ 12V jumpers. Have motor running and spray Seafoam into pump intake (not just the engine air stream in general). Like the takeoff fitting at bottom of air box or wherever yours is. Or, use the tube they give you and spray it into pump output somehow on its way to the combi valves. The idea is to get that solvent in there all the way through the combi valves and out to the passages into the exhaust. Afterward, the Italian tune up drive. Clear codes and see if any better.
Last edited by MP4.2+6.0; 06-18-2017 at 01:26 PM.
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06-18-2017, 11:08 PM
#8
AudiWorld Member
Thread Starter
I think if you dig into how the readiness codes work on OBDII you may get better info.
First, check the codes with VCDS and see if indeed the code in the 5th digit for SAI is where the issue is. See table at end of this reply for how to interpret.
Next, realize that if the readiness code is showing not ready, car will throw a CEL if it goes two cold hot cold cycles and can't confirm correct function. Some throw CEL right away, but ones like SAI and EVAP get basically two driving cycle cracks at it before it goes CEL.
Then, realize the test it is running is apparently not a cold test like I believe is what you are probably thinking, but rather one run at a certain rpm while you are driving at a fair steady speed. I think what it probably does is cycle the pump and then look at the O2's for a lambda change at a given RPM and mixture. If it does not see it, it concludes flow is no good. I suspect this is why you are seeing the CEL when driving as opposed to at cold start up. That's my experience IIRC when I have had SAI issues. See link to an attached document from Snap On for various older Audis and how to simulate the driving cycles to reset readiness codes. https://www1.snapon.com/Files/Diagno...CodeCharts.pdf It does cover the V8's from D2 era, but not D3 era. Bentley or somewhere else on web might yield you one specific to your motor. But may not matter; the point is I don't think readiness code for SAI is generated at cold start, and if you indeed find a not ready flag for SAI you will at least understand why and how the CEL is showing up.
The above just helps explain diagnostically what is going on w/ system, but doesn't solve your issue. Skimming through your latest reply, as ideas try:
First, check the codes with VCDS and see if indeed the code in the 5th digit for SAI is where the issue is. See table at end of this reply for how to interpret.
Next, realize that if the readiness code is showing not ready, car will throw a CEL if it goes two cold hot cold cycles and can't confirm correct function. Some throw CEL right away, but ones like SAI and EVAP get basically two driving cycle cracks at it before it goes CEL.
Then, realize the test it is running is apparently not a cold test like I believe is what you are probably thinking, but rather one run at a certain rpm while you are driving at a fair steady speed. I think what it probably does is cycle the pump and then look at the O2's for a lambda change at a given RPM and mixture. If it does not see it, it concludes flow is no good. I suspect this is why you are seeing the CEL when driving as opposed to at cold start up. That's my experience IIRC when I have had SAI issues. See link to an attached document from Snap On for various older Audis and how to simulate the driving cycles to reset readiness codes. https://www1.snapon.com/Files/Diagno...CodeCharts.pdf It does cover the V8's from D2 era, but not D3 era. Bentley or somewhere else on web might yield you one specific to your motor. But may not matter; the point is I don't think readiness code for SAI is generated at cold start, and if you indeed find a not ready flag for SAI you will at least understand why and how the CEL is showing up.
The above just helps explain diagnostically what is going on w/ system, but doesn't solve your issue. Skimming through your latest reply, as ideas try:
1. Pressure test your pump, even if changed. If you still have old one, maybe check it too. Check output against specs provided for system in Bentley or otherwise.
2. Recheck air plumbing between pump and the combi valves. I have seen that hose get soft over the years. I think if it leaks before a combi valve--even after wherever the split/tee is after the pump but before the combi valves--it may code to both sides like you are seeing.
3. Look critically at your suction side hose to pump. On my W12 it comes out of the bottom of the driver's side air box--it does that so it can pull air already filtered by main engine air filter. One time when I pulled fender liner I found thay hose was physically kinked and squeezed under my air box from some prior service work. Something like that would starve pump air intake and thus flow even if pump is good.
4. Get pump to cycle with VCDS--or just power it directly w/ 12V jumpers. Have motor running and spray Seafoam into pump intake (not just the engine air stream in general). Like the takeoff fitting at bottom of air box or wherever yours is. Or, use the tube they give you and spray it into pump output somehow on its way to the combi valves. The idea is to get that solvent in there all the way through the combi valves and out to the passages into the exhaust. Afterward, the Italian tune up drive. Clear codes and see if any better.
Finally, yes agreed w/ some of your commentary about the codes showing on both banks and what that may signify. To me that says probably look more at what is common to both banks, which to me says pump and related plumbing.2. Recheck air plumbing between pump and the combi valves. I have seen that hose get soft over the years. I think if it leaks before a combi valve--even after wherever the split/tee is after the pump but before the combi valves--it may code to both sides like you are seeing.
3. Look critically at your suction side hose to pump. On my W12 it comes out of the bottom of the driver's side air box--it does that so it can pull air already filtered by main engine air filter. One time when I pulled fender liner I found thay hose was physically kinked and squeezed under my air box from some prior service work. Something like that would starve pump air intake and thus flow even if pump is good.
4. Get pump to cycle with VCDS--or just power it directly w/ 12V jumpers. Have motor running and spray Seafoam into pump intake (not just the engine air stream in general). Like the takeoff fitting at bottom of air box or wherever yours is. Or, use the tube they give you and spray it into pump output somehow on its way to the combi valves. The idea is to get that solvent in there all the way through the combi valves and out to the passages into the exhaust. Afterward, the Italian tune up drive. Clear codes and see if any better.
Thank you MP4.2+6.0. Those are good suggestions that give me something to go on. This is proving to be one of those troublesome issues that seems to have no easy solution. The thing about it is that it does not affect drivability of the car, just an annoyance because of having to reset the code all the time. Makes sense what you are saying about warm run test. I just did not know the CEL function was that smart. I guess I assumed it was throwing codes in real time.
I'll have to check on the 5th code digit.
1) New pump is factory and I don't think old pump was faulty. The symptoms are the exact same with new pump as old. Nice thing is I have the old pump and seafoam trick can be used with old pump.
2&3) All hoses are new. Pretty sure they are all good and routed correctly. I've checked and rechecked them, and done pressure test.
4) I will install old pump and route seafoam from old pump air inlet. This way I will not damage new pump.
Question? Does running seafoam through the SAI system into the exhaust manifold and the cats risk any damage to those components, especially the O2 sensors or the cats?
Finally, it is a tricky problem because it can take several weeks sometimes before I get the code again after doing work. Usually less than a week, but I have gone 2 weeks driving before the code is thrown again.
Last edited by DA8; 06-18-2017 at 11:18 PM.
06-19-2017, 06:49 AM
#9
AudiWorld Super User
On your question about Seafoam, no guarantees if you will on the one hand. But obviously it has been around. The Mini guys have been using it for years for FSI related fouling issues--one of the Ground Zero motors for fouling. Did it myself a couple of times and zero issues with any emissions equipment, though I was spraying it into intake--after the MAF. Did help my FSI knocking sound issues though. You get a big cloud out of exhaust ultimately, though more so in my experience after you are done and then rev the motor or drive it to really blow everything through.
Maybe another data point is my C5 4.2 developed a big oil burning issue due to a damaged lower cylinder wall in one cylinder. Only fix was a new block, on a car that got to old to have enough value to get a replacement motor. It would eat a quart of oil every 250-500 miles if you drove a lot in town even with heavy weight oils I switched to--high vacuum pull is when it got worse. When it got super hot (100+F) and stuck in stop n go, it could turn into a cloud machine--to where you would shut motor down when stopped to avoid the issue (and the embarrassment). Even with all that oil passing by the cat and O2's on one side, it never poisoned either. That went on for the better part of 5 years; it would pass smog check with the older probe type up the exhaust, even blowing some smoke during the test. Thus from that experience, hard for me to believe that essentially one can of a light oil and solvent material is going to affect it much after probably 1000x + that went through my A6 exhaust system for years.
Maybe another data point is my C5 4.2 developed a big oil burning issue due to a damaged lower cylinder wall in one cylinder. Only fix was a new block, on a car that got to old to have enough value to get a replacement motor. It would eat a quart of oil every 250-500 miles if you drove a lot in town even with heavy weight oils I switched to--high vacuum pull is when it got worse. When it got super hot (100+F) and stuck in stop n go, it could turn into a cloud machine--to where you would shut motor down when stopped to avoid the issue (and the embarrassment). Even with all that oil passing by the cat and O2's on one side, it never poisoned either. That went on for the better part of 5 years; it would pass smog check with the older probe type up the exhaust, even blowing some smoke during the test. Thus from that experience, hard for me to believe that essentially one can of a light oil and solvent material is going to affect it much after probably 1000x + that went through my A6 exhaust system for years.
06-24-2017, 01:29 PM
#10
AudiWorld Member
Thread Starter
Here are the codes,
Address 01: Engine Labels: 077-910-560-BFM.clb
Part No SW: 4E0 910 560 J HW: 4E0 907 560
Component: 4.2L V8/5V G 0010
Revision: -------- Serial number: AUX3Z0D7748105
Coding: 0007773
Shop #: WSC 02313 785 00200
VCID: 2855EF9B9B27BF0181-807C
2 Faults Found:
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
Readiness: 0000 0000
Address 01: Engine Labels: 077-910-560-BFM.clb
Part No SW: 4E0 910 560 J HW: 4E0 907 560
Component: 4.2L V8/5V G 0010
Revision: -------- Serial number: AUX3Z0D7748105
Coding: 0007773
Shop #: WSC 02313 785 00200
VCID: 2855EF9B9B27BF0181-807C
2 Faults Found:
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
Readiness: 0000 0000