Engine - MIL ON, P0491 and P0492 Stored at Same Time
01 MIL on (P0491 and P0492 stored at same time)
01 13 83
2033001/1
March 29, 2013
Vehicle Information
Condition
^ MIL on.
^ DTC P0491 and P0492 (Secondary Air System Insufficient Flow, Bank 1/2) are stored at the same time.
^ Mileage is greater than 15,000 miles.
Technical Background
Under certain driving conditions, the secondary air ports in the cylinder head can accumulate carbon over time causing a restriction.
Production Solution
Not applicable.
Service
Tip:
This TSB will be updated soon. Please use the latest revision.
For Q5, S4 and A6 3.0T, follow the steps below. For A6 3.2AVS and Q7 3.0T, call Technical Assistance Center (TAC). Please note that before
performing this repair for the first time, it is mandatory that the technician complete Audi Academy Course # 940134 and assessment # 940134B,
otherwise the warranty claim will be denied. The course and assessment can be found on the Audi Academy CRC site. Specific video sections are
reference in the instructions below.
Perform VAS Testing
1. Delete all DTCs and bring the engine to operating temperature.
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2. Go into Basic Setting in the VAS tester (VSD) and select Secondary Air System Check.
3. Start the test on the VAS tester.
4. Depress the brake pedal first, followed by the gas pedal.
5. Record MVBs:
PRS_SA_DIF (record max value)
MASS_SA_REL (recode value at the end of test)
^ If PRS_SA_DIF max pressure is below 170mbar, follow GFF for these DTCs.
^ If max value of PRS_SA_DIF is greater than 170mbar / hPa and MASS_SA_REL below 0.6, the secondary air ports have to be cleaned.
Follow the steps below.
Tip:
To restart the test, back out of VSD to the main screen and cycle the key.
Prepare for Power Washing
1. Move the exhaust sliding bushings (that connect the catalytic converter and muffler) back, then lower the catalytic converter pipes (Figure 1).
Cleaning water will drain out of the catalytic converter pipes during the cleaning process.
2. Remove all spark plugs.
3. Drain the coolant so that it can be reused.
4. Bring front end of the car into service position (for Q5, A6, S4, and S5 Cabrio) to make room in the front of the engine. The Q7 has enough
room for access to the front of the cylinder heads.
5. For 3.0T only:
remove the coolant supply lines (intercooler of supercharger) in the front of the engine (Figure 2).
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6. Remove the following components:
^ Coolant pipe (Figure 3,1)
^ Coolant flange (Figure 3,2)
^ Pulley and if needed bracket, of power steering pump (Figure 3,3)
^ Pulley of water pump (Figure 3,4)
^ Coolant tube (Figure 3,5)
^ Dipstick tube (Figure 3,6)
Note:
When removing the dipstick tube, turn it 180 degrees, then reinstall it for water protection.
Note:
To loosen the coolant tube, remove 2 bolts (Figure 4, A and C), open clip (Figure 4, B), and pry bushing apart as shown in training video
(Figure 4, D). There is no need to loosen the AC compressor.
Cover opening of right coolant pipe to prevent coolant circuit contamination.
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7. Remove main port freeze plug by hitting the marked area with a small punch until it turns (Figure 5). Remove with pliers.
Prepare to Power Wash
Warning:
^ Read pressure washer user manual and follow these safety instructions.
^ Always insert special cleaning hose into adaptor and engine before turning pressure washer on.
^ If switching special cleaning to a different port, turn pressure washer off and release residual pressure by pulling the trigger before removing
the special cleaning hose from the engine.
^ Wear safety glasses and gloves.
1. Become familiar with the special tool set VAS6825 (Figure 6):
^ Special hose with scale for cleaning single ports (Figure 6,1)
^ Special hose for cleaning the main ports (Figure 6,2)
^ Hose adaptor for the special hose with scale (Figure 6,3)
^ Engine adaptor for bank one (Figure 6, 4a)
^ Engine adaptor for bank two (Figure 6, 4b)
2. To catch water, put a pan under the front of the engine and under the disconnected catalytic converter pipes.
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3. Install engine adaptors on the appropriate banks (Figure 7, Figure 8).
4. To ensure proper pressure washer function use a 3A inch water supply hose (no longer than 60 feet) to supply pressure washer.
The Audi-supplied pressure washer comes with a 22mm male-to-male adapter (to connect special tool to trigger gun), a pressure gauge (to
connect between pressure washer and high pressure hose), and a 220V power adapter.
Make sure that pressure is at least 1800 psi when using the special single port cleaning hose (the hose with the scale). Use the table shown to
compensate for low water pressure:
Power Wash the Ports
Cleaning Main Secondary Port:
1. Insert special main port cleaning hose (the hose without the scale) two inches into the engine adaptor.
2. Turn the pressure washer on.
3. Holding the cleaning hose tightly, pull the pressure washer trigger.
4. Gradually move the cleaning hose into the port, going back and forth until the combi valve is reached. All water comes out at the adaptor # 4.
5. Continue going back and forth through the whole port until only clean water drains out of the cylinder head.
6. Do the same with the other cylinder head.
Cleaning Single Ports:
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1. Because every port has a different distance to the cylinder head, use the table shown to position the hose adaptor for the special single port
cleaning hose (the hose with the scale) correctly into the hose. The back side of the hose adaptor must align with the number on the scale of the
cylinder to be cleaned (Figure 9). The longitudinal slot on the hose adaptor must align with the black line on the scale for correct rotational
positioning (Figure 9).
2. After adjusting the position of the hose adaptor, insert the special single port cleaning hose into the hose adaptor, and bring it back into locking
position (Figure 10).
3. While cleaning, make sure that the pressure washer is supplying pressure greater than 1800 psi.
4. Based on the washer's pressure, clean the port based on the table shown. While cleaning, continuously move the hose adaptor within the
longitudinal and transvers slots (Figure 10).
Tip:
After ten seconds of cleaning, all of the water should be draining out of the exhaust. If water is draining out of the engine adaptor, check the position
of the hose adaptor on the hose.
5. Do the same for all remaining cylinders.
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6. It is recommended that after cleaning, all single ports are checked with snap-on boroscope BK6000 (or similar, with 90-degree lens), to make
sure all ports are clean (Figure 11).
7. When all carbon is removed, install a new main port plug using an 8mm socket with a short extension, paying special attention to install it
squarely. The outer edge of the plug should be recessed 0.5mm - 1mm behind the outer cylinder head edge.
8. Reinstall all components (except spark plugs) and fill system with coolant according to ELSA.
9. Using a vacuum extractor, remove all water from all combustion chambers.
10. Make sure all water is removed from the combustion chambers by using the self-start function twice while the spark plugs are still removed
(cover spark plug openings with a towel). Install spark plugs and coils.
Make sure water is completely drained out of exhaust (make sure the exhaust is lowered enough).
11. Let the car run at idle for 15 minutes so all remaining water in the exhaust system can evaporate.
12. Perform VAS testing again, following instructions above.
^ Recode MVB MASS_SA_REL. If value is greater than 0.8 the system is ok.
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Warranty
All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures Manual. Claims are subject to
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review or audit by Audi Warranty.
