Technical Service Bulletin
01 MIL on, DTC P0491 and P0492 stored at the same time in the ECM
01 18 93 2033001/16 November 30, 2018. Supersedes Technical Service Bulletin Group 01 number 18-79 dated
July 12, 2018 for reasons listed below.
Model(s)

Year

VIN Range

Vehicle-Specific Equipment

A6

2009 - 2016

All

3.2 FSI AVS and 3.0 TFSI

A7

2013 - 2016

All

3.2 FSI AVS and 3.0 TFSI

S4

2010 - 2012

All

3.2 FSI AVS and 3.0 TFSI

A8, Q7

2011 - 2016

All

3.2 FSI AVS and 3.0 TFSI

A5, S5
Cabriolet,
and Q5

2010 - 2016

All

3.2 FSI AVS and 3.0 TFSI

Condition
REVISION HISTORY
Revision

Date

Purpose

16

-

Revised header data (Added model)
Revised Warranty (Updated Labor Operations and Diagnostic Time)
Revised Required Parts and Tools (Added A8)

15

07/12/2018

Revised title
Revised Required Parts and Tools (Clarification on gasket)

14

08/17/2017

Revised Required Parts and Tools (Added Power Steering Fluid)

Customer states:
 MIL on.
Workshop findings:
Both of the following DTCs are stored in the engine control module (ECM), J623 (address word 0001):
 DTC P0491 (Secondary Air System Insufficient Flow, Bank 1).
 DTC P0492 (Secondary Air System Insufficient Flow, Bank 2).
 Mileage is greater than 15,000 miles.

Technical Background
Page 1 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
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
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 referenced in
the instructions below.
Perform ODIS Testing – For all but A6 (C6) 3.2FSI and Q7 3.0T:
1. Delete all DTCs. Bring the engine to operating temperature.
2. Go to Control Modules >> 01 Engine Control Module >> Control module OBD>> Basic Settings >> Checking
Secondary Air System.
3. Select MVB: MASS_SA_REL[0] and MASS_SA_REL[1].
4. Perform test (Press brake and gas pedal at the same time, start test on ODIS tester).
5. While Basic Setting test is running, check if the secondary air pump runs normally (no unusual noises). In
addition, check for a leak in the secondary air hose routing between the pump and combi valves.
6. Immediately after the test is complete, read MASS_SA_REL[0] and MASS_SA_REL[1]. Depending on the
software level and engine code, the air mass flow will be displayed in one of two ways:
 For old software version:
If the value is between 0.1 and 0.7, and there were no issues with the pump and hoses, the system needs
to be cleaned. Follow the instructions below.
 For new software version:
If the value is between 13 and 16, and there were no issues with the pump and hoses, the system needs
to be cleaned. Follow the instructions below.

Perform ODIS Testing – For A6 (C6) 3.2FSI and Q7 3.0T only:
1. Go to Control Modules >> 01 Engine Control Module >> Control module OBD>> Basic Settings >> test 77.
2. While performing test 77, check if the secondary air pump is running and make sure it does not make any
abnormal or unusual noise:

Page 2 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
 If test 77 fails but the pump is running and does not make any abnormal/unusual noise, perform the
cleaning process below.
 If the pump is not running or if it makes abnormal/unusual noise, this TSB does not apply.
Tip: Always use the latest version of this TSB.

Prepare the Vehicle for Power Washing:
1. Move the exhaust sliding bushings
(that connect the catalytic converter
and muffler) back, then lower the
catalytic converter pipes (Figure 7).
For Q7, unbolt muffler from catalytic
converter. Cover mufflers with plastic
bag to prevent water from entering.
Cleaning water will drain out of the
catalytic converter pipes during the
cleaning process.

Figure 7. Lowered catalytic converter pipes.
2. Remove all spark plugs and cover the engine harness plugs for the coils (for water protection).
3. Drain the coolant so that it can be reused.
4. Bring front end of the car into service position (for Q5, A6, A8, S4, and S5 Cabriolet) to make room in the
front of the engine. The Q7 has enough room for access to the front of the cylinder heads.

Page 3 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
5. For 3.0T only: remove the coolant
supply lines (intercooler of
supercharger) in the front of the
engine (Figure 8).

Figure 8. Front coolant pipes to be removed for 3.0T.
6. Remove the following components:
 Coolant pipe (Figure 9, image 1).
 Coolant flange (Figure 9, image
2).
 Pulley and if needed bracket, of
power steering pump (Figure 9,
image 3).
 Pulley of water pump (Figure 9,
image 4).
 Coolant tube (Figure 9, image 5).
 Dipstick tube (Figure 9, image 6).

Figure 9. Engine component removal.
Note:
When removing the dipstick tube, turn it 180 degrees, and then reinstall it for water protection.

Page 4 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
Note:
To loosen the coolant tube, remove 2 bolts (Figure 10, image A and C), open
clip (Figure 10, image B), and pry bushing apart as shown in training video
(Figure 10, image D). There is no need to loosen the AC compressor.
Cover opening of right coolant pipe to prevent coolant circuit contamination.

Figure 10. Loosening the
coolant tube.
7. Remove main port freeze plug by
hitting the marked area with a small
punch until it turns (Figure 11).
Remove with pliers.

Figure 11. Marked area on main port of freeze plug.

Prepare to Power Wash Tool Setup:

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 12):

Page 5 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
 Special hose with scale for cleaning
single ports (Figure 12, image 1).
 Special hose for cleaning the main
ports (Figure 12, image 2).
 Hose adaptor for the special hose
with scale (Figure 12, image 3).
6  Engine adaptor for bank one (Figure
12, image 4a).
 Engine adaptor for bank two (Figure
12, image 4b).

Figure 12. Special tool set VAS6825.
2. To catch water, put a pan under the front of the engine and under the disconnected catalytic converter pipes.
3. Install engine adaptors on the
appropriate banks (Figure 13 and Figure
14).

Figure 13. Engine adaptor on bank one.

Figure 14. Engine adaptor on bank two.

Page 6 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
4. To ensure proper pressure washer function, use a ¾-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 below to compensate for low water pressure:

psi While Cleaning Single Ports

Cleaning Time in Minutes

Less than 1900

Pressure too low – check water supply

1900

4

2000 or higher

3

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:
1. Because every port has a different distance to the cylinder head, use the table below 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 15).
The longitudinal slot on the hose adaptor must align with the black line on the scale for correct rotational
positioning (Figure 15).

Dimensions Port 1

2

3

Page 7 of 13
© 2018 Audi of America, Inc.
All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other intellectual property rights of Audi of
America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may these materials be modified or reposted to other sites, without the prior expressed written permission of the
publisher.

Technical Service Bulletin
Bank One

10.5

19.5

28.5

Bank Two

13.7

22.7

31.8

Figure 15: Arrow indicating how the back side of the adaptor must align with the scale. Red dotted line
indicating how the longitudinal slot must align with the black line on the scale.

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 16).

Figure 16. Locking position / transvers longitudinal
movement and of the hose adaptor
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 below. While cleaning, continuously move
the hose adaptor within the longitudinal and transvers slots (Figure 16).

Psi While Cleaning Single Ports Cleaning Time in Minutes
Less than 1900

Pressure too low – check water supply

1900

4