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Discussion Starter #1
Hey guys, I need a little help. I have Codes P0491 and P0492 coming up for my 04 V8. Now I know that both are for the secondary air system bank 1 and 2 but how do I pin point the problem my self? At first I thought it may have been a carbon build up but I think that’s more of an FSI issue. So that being out, I don’t see why I can’t do the work my self ( famous last words lol) so where and what do I look for? Thanks guys.


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Had this problem on my Audi S6 4.2 V8, but only on one side. My problem was a dry-rotted vacuum hose. A little tricky to route back to the vacuum source, but an easy replacement with some hose from the local auto parts store. That was the common failure on that engine in the A6 line.

Matt


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Could be a bunch of things.... I assume you can't get scanned with a proper VCDS?

P0491 - Secondary Air Injection System: Bank 1
P0491 - Secondary Air Injection System: Bank 1: Insufficient Flow
Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Fuse or relay for Secondary Air Injection Pump faulty
Hose(s)/Piping between Secondary Air Injection Pump and Combi (Secondary Air Injection) Valve leaking
Secondary Air Injection Solenoid(s) faulty
Secondary Air Injection Pressure Sensor faulty
Combi Valve(s) faulty
Secondary Air Injection ports in the cylinder head(s) plugged with carbon See Special Notes
Possible Solutions
Check fuse and relay for Secondary Air Injection Pump system.
Check hose(s)/Piping between Secondary Air Injection Pump and Combi Valve
Check Secondary Air Injection Solenoid(s)
Check Secondary Air Injection Pressure Sensor
Check Combi Valve(s)
Clean Secondary Air Injection ports in the cylinder head(s) if obstructed with carbon See Special Notes
Special Notes
When found in the following NAR (North American Market) Audi models listed below check to see if TPI 2033001 is applicable:
Audi TPI 2033001 pertains to P0491 and P0492 stored at same time on the following vehicles with more than 15,000 miles:
2010+ S4 and S5 with CCBA 3.0L
2008+ A5, 2009+ A4, 2011 A6 with CALA 3.2L
2009-2011 A6 CCAA 3.0L
2012 A6/A7 CGXB 3.0L
2013+A6/A7 CTUA 3.0L
2009+ Q5 CALB 3.2L
2011+ Q7 CJWE, CJWC, CJWB 3.0L
P0492 - Secondary Air Injection System: Bank 2
P0492 - Secondary Air Injection System: Bank 2: Insufficient Flow
Possible Symptoms
Malfunction Indicator Light (MIL) active
Possible Causes
Fuse or relay for Secondary Air Injection Pump faulty
Hose(s)/Piping between Secondary Air Injection Pump and Combi (Secondary Air Injection) Valve leaking
Secondary Air Injection Solenoid(s) faulty
Secondary Air Injection Pressure Sensor faulty
Combi Valve(s) faulty
Secondary Air Injection ports in the cylinder head(s) plugged with carbon See Special Notes
Possible Solutions
Check fuse and relay for Secondary Air Injection Pump system.
Check hose(s)/Piping between Secondary Air Injection Pump and Combi Valve
Check Secondary Air Injection Solenoid(s)
Check Secondary Air Injection Pressure Sensor
Check Combi Valve(s)
Clean Secondary Air Injection ports in the cylinder head(s) if obstructed with carbon See Special Notes
Special Notes
When found in the following NAR (North American Market) Audi models listed below check to see if TPI 2033001 is applicable:
Audi TPI 2033001 pertains to P0491 and P0492 stored at same time on the following vehicles with more than 15,000 miles:
2010+ S4 and S5 with CCBA 3.0L
2008+ A5, 2009+ A4, 2011 A6 with CALA 3.2L
2009-2011 A6 CCAA 3.0L
2012 A6/A7 CGXB 3.0L
2013+A6/A7 CTUA 3.0L
2009+ Q5 CALB 3.2L
2011+ Q7 CJWE, CJWC, CJWB 3.0L
 

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Discussion Starter #4
Had this problem on my Audi S6 4.2 V8, but only on one side. My problem was a dry-rotted vacuum hose. A little tricky to route back to the vacuum source, but an easy replacement with some hose from the local auto parts store. That was the common failure on that engine in the A6 line.

Matt


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What Hoses did you look at? I don't even know where the secondary air pump is
 

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Tman33, do a smoke test, it will show you where the leak is. On my FSI, I hook smoker up to vacuum line coming off brake boost vacuum.


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I feel like its prob a hose some where. Maybe a fuse? What fuse is it?
I feel like you should troubleshoot properly, with proper tools instead of randomly guessing.... unless you have time and money to waste.... but that's just me.

Do you live in the woods? You clearly have internet service, so surely there must be someone around with a VCDS that will provide a proper scan for you in exchange for a coffee or something.... or am I reaching for the stars here? :wink2:
 

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Tman33, do a smoke test, it will show you where the leak is. On my FSI, I hook smoker up to vacuum line coming off brake boost vacuum.


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OP,

^^This is what you want to start. The plastic vacuum lines crack and leak due to old age. The problem is the vacuum lines still look good.

The quickest way to fix is (1) to replace every vacuum line or (2) to find the existing leaks to fix, using the smoke test.

The 04 05 06 V8 is the older V8. Engine code AXQ and used fuel injectors that spray at the intake valves. It does not have massive carbon buildup problems that the later 07 and 08 direct fuel injected Touareg V8 did.

The 04 05 06 do have a timing belt to deal with. The 07 and 08 used a timing chain.

Just a side note. Tear down the earlier engine for the timing belt or tear down the later engine to de-carbon. It didn't matter which V8 you have, sooner or later you will be taking it apart.
 

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Discussion Starter #11
I feel like you should troubleshoot properly, with proper tools instead of randomly guessing.... unless you have time and money to waste.... but that's just me.



Do you live in the woods? You clearly have internet service, so surely there must be someone around with a VCDS that will provide a proper scan for you in exchange for a coffee or something.... or am I reaching for the stars here? :wink2:


I actually live under a rock haha. ButIts not a pressing issue, just thought if it was something simple mine as well. I’ll try to find someone to scan it. Or really I should just pick up a Vag since I have 4 Vag cars


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Discussion Starter #13
OP,



^^This is what you want to start. The plastic vacuum lines crack and leak due to old age. The problem is the vacuum lines still look good.



The quickest way to fix is (1) to replace every vacuum line or (2) to find the existing leaks to fix, using the smoke test.



The 04 05 06 V8 is the older V8. Engine code AXQ and used fuel injectors that spray at the intake valves. It does not have massive carbon buildup problems that the later 07 and 08 direct fuel injected Touareg V8 did.



The 04 05 06 do have a timing belt to deal with. The 07 and 08 used a timing chain.



Just a side note. Tear down the earlier engine for the timing belt or tear down the later engine to de-carbon. It didn't matter which V8 you have, sooner or later you will be taking it apart.


Every line ? Yikes haha


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Discussion Starter #15
Any TSB? I know some of the VAG engine are notorious for the secondary air ports on the heads blocking up.


I know for a fact that Audi actually covers it up to a 120k for the 3.0T. Ask me how I know


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What Hoses did you look at? I don't even know where the secondary air pump is

Mine were problems with the braided hoses on the front of the engine (hose 5, 6, 7, IIRC - its been years), this was from an 03 S6 which is a little different than the more standard 4.2 V8, but the vacuum hose routing looks familiar.

This article shows how to gut it and replace them all. If you have the braided cover hose still on your engine, I’d replace it regardless. It is very likely dry-rotted and you’ll have a variety of drivability issues. I’m going to guess I had that CEL before the car was at 100K and I ran it to 200K.

I’m curious how similar the build on the T is compared to the Audis with this engine.

http://www.audipages.com/Tech_Articles/enginemechanical/vacuumhosereplace.html


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