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post #1 of 19 Old 04-02-2019 Thread Starter
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Help P0491-P0492

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 thatís more of an FSI issue. So that being out, I donít see why I canít do the work my self ( famous last words lol) so where and what do I look for? Thanks guys.


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post #2 of 19 Old 04-02-2019
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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.

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post #3 of 19 Old 04-02-2019
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Could be a bunch of things.... I assume you can't get scanned with a proper VCDS?

Quote:
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
Quote:
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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post #4 of 19 Old 04-02-2019 Thread Starter
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Quote:
Originally Posted by woodster5000 View Post
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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post #5 of 19 Old 04-02-2019 Thread Starter
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Quote:
Originally Posted by TurboABA View Post
Could be a bunch of things.... I assume you can't get scanned with a proper VCDS?
I feel like its prob a hose some where. Maybe a fuse? What fuse is it?
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post #6 of 19 Old 04-02-2019
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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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post #7 of 19 Old 04-02-2019
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Quote:
Originally Posted by Touaregman33 View Post
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?
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post #8 of 19 Old 04-02-2019
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Or this
Attached Files
File Type: pdf vw.tb.00-05-09 MIL Is On, DTC's P1411,P1423 Stored.pdf (228.6 KB, 13 views)
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post #9 of 19 Old 04-02-2019
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Quote:
Originally Posted by mtnride View Post
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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post #10 of 19 Old 04-02-2019 Thread Starter
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Quote:
Originally Posted by mtnride View Post
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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Smart smart!


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