Never Ending Check Light - Secondary Air Injection
07-19-2018, 03:51 PM
#31
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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!
I have a 2012 Audi A8 l and the same problem.. Replaced everything.. and it still comes on for 10 days.. goes off for 4 days randomly.. Initially the yellow light would stress me out.. but of late I have begun to ignore it.. The car runs great.. Did you ever get this fixed ? Thanks!
07-21-2018, 05:41 AM
#32
AudiWorld Member
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!
07-21-2018, 07:33 AM
#33
AudiWorld Super User
This sounds like an electrical issue to me. Degraded wiring, connection issues, solder let go, or something like that. Just the intermittent nature of it and the difficulty solving it despite looking at most of the components.
07-22-2018, 03:29 PM
#34
AudiWorld Senior Member
I like reading a post that requires 4 or 5 Audi type Sherlock Holmes' and Jerry-rigged MacGyver solutions. As for the "no space" to get the Combi bolts out I have a tool that would help. Many years ago I worked on computer hardware (printers card readers, etc). This is when computers utilized vacuum tubes, if anyone knows what they were. For working in tight spaces, my tool box had a "Chapman" set. I always referred to it as my "Mission Impossible tool" because it allowed access to tight spaces. I used it lst year to remove screws that held the ABS module on the brake modulator. My set had a bunch of short, 1/4" bits like the ones you use with a drill driver, except shorter. For my ABS module, I used a Torx bit that I shortened to be flush with the back of the ratchet tool. My shortened bit did not have the little ball bearing that holds the bit in the ratchet and yes, it fell out a enough to be a PITA. A strategically placed magnet helped.
I didn't even know they still made the tool, Back in the day, there were no Torx bits but when searching Chapman to find a picture, I see they make Torx bits for it. They also make metric hex bits which I understand is needed for the Combi valve. Like my Jerry rigged Torx bit, the metric hex could be shortened to get it down slightly less than 1" depth.
Rather than try to describe it, here is a link to Chapman with detail pictures of the ratchet and bits.
https://www.newmantools.com/chapman/
Over the years, my Mission Impossible tool has come in handy. As for hands, mine are closer to that of a bear, but the tool really helped.
I didn't even know they still made the tool, Back in the day, there were no Torx bits but when searching Chapman to find a picture, I see they make Torx bits for it. They also make metric hex bits which I understand is needed for the Combi valve. Like my Jerry rigged Torx bit, the metric hex could be shortened to get it down slightly less than 1" depth.
Rather than try to describe it, here is a link to Chapman with detail pictures of the ratchet and bits.
https://www.newmantools.com/chapman/
Over the years, my Mission Impossible tool has come in handy. As for hands, mine are closer to that of a bear, but the tool really helped.
Last edited by audijim113; 07-22-2018 at 03:32 PM.
07-22-2018, 05:32 PM
#35
AudiWorld Member
DA8,
just curious, in your pics, that plastic splash shield under your transmission pan between the two pipes... Mine is attached just to the splash shield in front of it , and it droops down. How is yours so snug with the car? Is it screws onto something other than the splash shield in front of it??
just curious, in your pics, that plastic splash shield under your transmission pan between the two pipes... Mine is attached just to the splash shield in front of it , and it droops down. How is yours so snug with the car? Is it screws onto something other than the splash shield in front of it??
Last edited by Sci-fi_Wasabi; 07-23-2018 at 03:17 AM.
07-26-2018, 12:37 PM
#36
AudiWorld Wiseguy
It’s a very finicky system that is evidently a PITA to diagnose and fix. It’s powered by both the vacuum and electrical systems, and it doesn’t contain any sensors or direct diagnostic systems. Fault detection is reliant upon other outside systems to identify; namely small differences in the correlation between the MAF and the oxygen sensor readings. The most specific it gets is to which cylinder bank is affected. Then it’s a hunt through multiple systems, hoses and components as to what the specific fault may be.
For what it’s worth, I thought mine was fixed after having my bank 1 combi valve replaced. Annoyingly the same error has come back after a couple months. Fortunately I heeded advice and had my local specialist do the job, so the repair came with a warranty. So it’s his problem to fix now. I’d have been truly cursing at this point if I’d done the job myself.
Last edited by dvs_dave; 07-26-2018 at 12:40 PM.
07-28-2018, 11:40 AM
#37
AudiWorld Wiseguy
Emissions Readiness code generating > drive cycle procedure
So my indie stood by his word and replaced the duff “new” bank 1 combi valve at no cost to me.
My registration runs out end of this month and it has to pass emissions to renew. I’ve been desperately trying to get all the readiness codes set as they all need very specific drive cycle criteria to be met. The EVAP and SAI ones can take weeks if you typically only do short trips (I live downtown Chicago) with little to no ability to achieve steady state 50mph highway time for any length of time.
I took a gamble and thought a trip out to the suburban test center would do it, but alas, they were both still not ready when I got there so annoyingly a wasted trip.
Anyway, did some searching on how to set the readiness codes and came across this very good guide from snap-on tools. I followed this and, boom, all readiness codes set and passed. All it took was 3-5 mins of idling from a cold start to set the SAI code. All the others were already set. I can now pass emissions and renew my registration.
Anyway, guide below, and it proved extremely useful.
My registration runs out end of this month and it has to pass emissions to renew. I’ve been desperately trying to get all the readiness codes set as they all need very specific drive cycle criteria to be met. The EVAP and SAI ones can take weeks if you typically only do short trips (I live downtown Chicago) with little to no ability to achieve steady state 50mph highway time for any length of time.
I took a gamble and thought a trip out to the suburban test center would do it, but alas, they were both still not ready when I got there so annoyingly a wasted trip.
Anyway, did some searching on how to set the readiness codes and came across this very good guide from snap-on tools. I followed this and, boom, all readiness codes set and passed. All it took was 3-5 mins of idling from a cold start to set the SAI code. All the others were already set. I can now pass emissions and renew my registration.
Anyway, guide below, and it proved extremely useful.
Last edited by dvs_dave; 07-28-2018 at 11:48 AM.
05-16-2019, 08:44 PM
#38
AudiWorld Junior Member
Join Date: Dec 2010
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MAF replacement solved dual bank secondary air non-readiness for me.
... a marginal or non OEM MAF can also be the cause of a dual bank SAI error. The sensors that the ECU uses to run the SAI test are the MAF and the primary O2 sensor for each bank. A misreading MAF will then not correlate to what the o2 sensors are seeing, and throw a code. And given what I think are fairly small o2 changes it’s looking for, it’s possible that it’s not picked up by the system until it’s specifically looking for a very specific change in readings during the SAI test.
05-17-2019, 04:22 AM
#39
AudiWorld Member
Thread Starter
Just catching up on this post. Yes, I still have the same problem, need to reset the code every few times I drive the car. I never have been able to solve it. I never did take the intake manifold off to clean its internals yet. I appreciate a lot of good comments here. Going on 9 years of ownership now and still love this car and it runs fantastic. Really trouble free overall. I replaced the front air struts last winter, it just keeps on being a great car as long as you keep up with maintenance. The SAI though has never been solved for me. Sure it does not affect drivability, but the light constantly returning drives me nuts.
That one cracked me up and had me laughing out loud. It is so true. If the world only appreciated our genius.
The reason I did not suspect MAF was that I had replaced it several years back. What lead to that was MP4.2 + 6.0 saying K&N oil coated filters slowly reduce HP by coating lightly the MAF with oil. Well, I had one in and thought I wouldn't know if my HP had been reduced. So I took out the K&N and replaced the MAF. Never had any issues with it since that I know of. So I hate to replace the expensive MAF not having any reason to suspect it has any problems. But what is being said here is it could be causing SAI trouble. My SAI fault is constant, meaning it will always come back on within a few drives. I drive a lot of 20-30 min runs on the freeway at 80MPH to Seattle, that seems to alway pop up the code.
midnightgolfer seems to have confirmed solving the problem with a new MAF, but did the light come back on after some time?
I never had any problem passing emissions. I just reset the code and it always passes the test no problem. But the light comes back on after a few drives, the reset just works long enough for the emission test.
Yes, the narrow plastic belly pan for the tranny is bolted on on both ends. In the pic I have the front bolts out and bend it down with the back bolts still attached.
I just thought I would chime in. I had both banks of secondary air injection giving me failed Readiness. (I couldn't pass Smog at the California Start Station to renew my registration) - I replaced my MAF and was immediately able to get secondary air injection to pass Readiness.
midnightgolfer seems to have confirmed solving the problem with a new MAF, but did the light come back on after some time?
I never had any problem passing emissions. I just reset the code and it always passes the test no problem. But the light comes back on after a few drives, the reset just works long enough for the emission test.
DA8,
just curious, in your pics, that plastic splash shield under your transmission pan between the two pipes... Mine is attached just to the splash shield in front of it , and it droops down. How is yours so snug with the car? Is it screws onto something other than the splash shield in front of it??
just curious, in your pics, that plastic splash shield under your transmission pan between the two pipes... Mine is attached just to the splash shield in front of it , and it droops down. How is yours so snug with the car? Is it screws onto something other than the splash shield in front of it??
05-17-2019, 05:52 AM
#40
2015 A8L TDI
What I learned from my BMW E38 friends is the Mass Air Flow sensor is a wear item.
A very long wear, a beyond the warranty wear, but it does wear over time nonetheless.
A very long wear, a beyond the warranty wear, but it does wear over time nonetheless.