N_Jay

2000 A6 2.8Q

Since this is insufficient secondary air flow to both banks, I would guess it has to be something in the common system such as the pump fuse or relay for some of the plumbing.
What problems have people found that caused these errors.
These codes showed up Suddenly no other errors before that.

Edit: fuse is good. Relay looks ok.

jcman

Stuck or inoperative Combi Valves are the usual suspect with these codes, much has been posted on that.

N_Jay

Those are essentially the EGR valves for each head? Right?

Wondering why both codes show up together?

How hard are they to change on a A6 2.8?

Worth trying to clean, at about$100 each?

jcman

No, the SAI system is not recirculating exhaust gas.

Two codes would also suggest a problem with the vacuum side that operates the combi valves.

Make sure they operate before ruling them out because they are a PITA to remove to clean or replace.

jcman

Secondary air injection seems to be something sooner or later every Audi owner has a problem with. Let me run down the symptoms and then the steps to fix them. This should be the definitive guide on how to repair the system.

The first and most common problem is broken/frayed vacuum lines that run to the kombi valve(s). If you have a 2.8, there was a recall on most of them to update the vacuum lines to beefier lines. If this wasn't you, or you have a 1.8, it's still easy to check the vacuum lines. If they even look suspect, just replace them. Vacuum hose is cheap enough and easy to change out. Vacuum lines don't last forever, and heat/age will wear them out.

The next thing to check for is an air pump that flows properly. With VAG-COM there are self diagnostic tests that will cycle the air pump on/off. If it makes a high pitch noise sort of like a jet engine, it may be due for replacement. The air pump typically kicks in when the car is running and idleing. It won't run constantly, usually for about 10 seconds and then shut it off. It's purpose is to pump air into the exhaust which helps improve catalysts when the cat isn't fully up to temp. I've even seen mine run even when the car is fully up to temp. YMMV.

Next on the list to check is the kombi valve(s). You can try and check for their functionality while still on the car, but this may be hit or miss. You need a hand vacuum pump to do this. Use the vacuum pump and pump it up to about -20. If you suddenly release the vacuum, and can feel/hear a nice little thunk from the valve, the diaphragm is probably fully opening and closing. If you don't hear or feel it, it could be sticking. What you want to do then is remove the kombi valve from the car. Use some brake cleaner, and spray it out with the valve both open and shut (use the hand pump). You should have a lot of carbon build up wash out. Operate it off the car and see if you can get smooth operations in the opening and closing. If you do, the valve is probably fine and you saved yourself from buying a new valve. If you are at this stage, it's best to engage in the next repair I have listed.

Carbon build up in the kombi valve exhaust passage is probably the hardest to diagnose. I have yet to see any Audi technician troubleshoot this or even attempt a guess at this could be the problem; but it was an issue on my car. I was able to track this down, but it took a little while. When my air pump ran, I could feel the idle get a little rougher. What I ended up doing was hooking only 1 kombi valve up at a time to the vacuum solenoid to see if I could figure out what side was the culprit. This worked. I was able to get a rough idle on 1 bank, and not on the other. Once I took off the kombi valve, I used a coat hanger to clean out the carbon in the air passage. I could feel a sizeable blockage near the entrance. I then used brake cleaner to clean the passage even more. Brake cleaner does a great job at disolving carbon. Use some spare vacuum hose (hard nylon line if you have it) to shove in the passage. Use the straw on the brake cleaner can, insert it in the hose, and spray away. Follow up with more coat hanger cleaning. Be careful not to break anything off or get something stuck in that passage way. If you do, you'll basically have to pull the head to try and get it out of there.

The last thing potentially that could be a problem is the solenoid for the vacuum lines. I have yet to seen these fail. The 2.8 has two of these actually. One for the kombi valves, one for the intake manifold. VAG-COM in it's self test mode will test these and you'll be able to hear them working.

So to summarize, check the vacuum hoses and replace first. Then check the air pump. Then check the kombi valves and carbon buildup.

N_Jay

It is getting a few easy tests, and then coded out.
All I need is to pass smog in July. Doubt the car is going to be in use in 2 more years.

jcman

Hopefully its just a vacuum hose.

N_Jay

That is where I am starting. right after making sure the pump runs.

Airbag

that wa gonna be my first question .. does the pump run ?

N_Jay

I have to figure that out, but seems I need a cold car and my son goes to work at 6 am, and I can't hear the fan from bed.