Error code p0491
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AudiWorld Member
Joined: Feb 2019
Posts: 146
Likes: 25
Error code p0491
Howdy all,
2011A8L 115000 miles 4.2
Today is the 1 year anniversary of owning my car! So of course this crap happens
Today about 2 minutes after starting my car (after sitting for about 4 hours 35 degree day) CEL came on. After reading the code (I don't have a vcds reader or anything more sophisticated) it returned p4091 secondary air intake bank issue.
I have two high level questions, the car ran fine driving home (35 minutes at a mixif highway and surface driving) is this a major fault I need to have addressed immediately? Tomorrow is a rather busy day, and if I can avoid it, I would prefer to not deal with the dealer
Second question is always cost. I know this is a non specific code cover like 8 parts and vacuum tubes, but has anyone delt with this before!?
Car has been running a peach otherwise.
As always, any help is truly appreciated!
2011A8L 115000 miles 4.2
Today is the 1 year anniversary of owning my car! So of course this crap happens
Today about 2 minutes after starting my car (after sitting for about 4 hours 35 degree day) CEL came on. After reading the code (I don't have a vcds reader or anything more sophisticated) it returned p4091 secondary air intake bank issue.
I have two high level questions, the car ran fine driving home (35 minutes at a mixif highway and surface driving) is this a major fault I need to have addressed immediately? Tomorrow is a rather busy day, and if I can avoid it, I would prefer to not deal with the dealer
Second question is always cost. I know this is a non specific code cover like 8 parts and vacuum tubes, but has anyone delt with this before!?
Car has been running a peach otherwise.
As always, any help is truly appreciated!
AudiWorld Member
Joined: Nov 2013
Posts: 300
Likes: 33
From: Great Lakes, IL
I had that issue with my S8 D3. I changed secondary air pump and it was a ok. Could be you have one of the hose loose but I doubt it. Second air circulation hoses are hidden pretty good to protect it from any kind of physical damage.
Thread Starter
AudiWorld Member
Joined: Feb 2019
Posts: 146
Likes: 25
Local indy shop says it is a minor fault that I could live with for years. They are getting the car this weekend to do some hunting, I will report back on what the actual cause is. The car seem to run just fine with it, just the annoying CEL on my dash 
Thanks!
Thanks!
AudiWorld Member
Joined: Dec 2015
Posts: 79
Likes: 2
From: Northern Virginia
I just had this code as well. When I went to take it to my mechanic, the engine light is no longer lit (of course). He works on it for a day, testing every component of the SAI system and tells me everything is working perfectly! He said he saw the stored 491 code, but not to worry about it. He thinks one of the "combination valves" might have been sticking and is now working. He also mentioned that Audi does have a TSB for this very issue, the resolution is to replace the combination valves with a newer version that is less prone to sticking. Out of warranty cost, something like $1,500. My mechanic advised to just keep driving it until it becomes a nuisance and then replace the valves.
AudiWorld Senior Member
Joined: Mar 2015
Posts: 1,597
Likes: 16
From: North Texas
I would start with new air filters. I had two different issues appear that went away with new air filters. Now I say that any lean error code resolvement should start with new air filters.
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