Technical Service Bulletin
27 48V Vehicle electrical system warning, DTC P0CA700 and/or U046900 stored in the starter/generator
control module/ECM
27 23 57 2058831/9 June 14, 2023. Supersedes Technical Service Bulletin Group 27 number 23-55 dated May 8,
2023, for reasons listed below.
Model(s)

Year

A6, A7, A8, and
Q8

2019 – 2024

A6 allroad, S8,
and Q7

2020 – 2024

A8 e quattro

2020 – 2021

VIN Range

Vehicle-Specific Equipment

All

48 V MHEV

Condition
REVISION HISTORY
Revision

Date

Purpose

9

-

Revised header (updated vehicle and PR number filter)

8

05/08/2023

Revised header (updated vehicle and PR number filter)

7

03/30/2023

Corrected publishing error

Customer states:
• The message “Electrical system: fault. See owner’s manual” is displayed on the instrument cluster.
• A yellow or red battery warning symbol is displayed on the instrument cluster.
Workshop findings:
One or more of the following DTC(s) may be stored:
Battery management 2 (Battery 48V) control module, J1120 (address word 0021):
• DTC P0CA700: Hybrid battery discharge current too high.
ECM, J623 (address word 0001), or Gateway, J533 (address word 0019):
• DTC U046900: Invalid data received from starter/generator control module (Symptom 36564).

Technical Background
The Belt Starter Generator (BSG), together with the vehicle’s 48V system is an intelligent vehicle system that
provides electrical power to the vehicle as needed. Therefore, traditional diagnosis methods, like expecting the

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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
alternator to output at full voltage any time the vehicle is running, are no longer viable, as the output power of the
BSG is regulated according to the current requirements of the vehicle.
For further in depth information, please refer to TSB 2067906: 27 48V Reference: diagnosis and system
information.
Criterion 1:
A software related issue may cause the belt starter generator (BSG) to stop working as intended.
Criterion 2:
A hardware related issue may cause the belt starter generator (BSG) to stop working as intended.

Production Solution
Criterion 1:
An optimized software has been implemented in current production vehicles.
Criterion 2:
Not Applicable.

Service
Check the extended ambient conditions for DTC U046900 Control unit for starter-alternator, implausible signal
that is stored in the engine control module, J623 (address word 0001), or the Gateway, J533 (address word
0019).
Criterion 1:
If the value displayed for Starter generator, actual mode 48V is not shown, or a value other than 5 is displayed
(see Figure 1) please check the software version of the BSG (address word 00CC).
If the software is older than, but not including SW 0527, please update the BSG via the SVM update instructions
at the end of this TSB, then follow up with the checks listed under Criterion 2.

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© 2023 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

Figure 1: Extended ambient data in ODIS GFF log.
Criterion 2:
If the value displayed for Starter generator, actual mode 48V is 5, or otherwise, if the software of the BSG already
is at SW 0527 or was updated under Criterion 1, perform the following diagnostic steps to determine if the belt
starter generator is the root cause of the customer complaint:
1. Select OBD in ODIS, then select 00CC - Starter Generator >> Measurement Values.
2. Select the following measurement values for display:
•

[IDE12494]_Voltages

• [IDE12495]_Torques
• [VO]_operation_mode
3. Disconnect the battery charger from the vehicle, and start the engine. The vehicle should idle in park.
4. Determine if the measurement values are within their specified tolerances:
[IDE12494]_Voltages
Voltage of terminal 87
Values between 11.6V and 15V are normal – If the voltage is below 11.6V, please recharge or replace the
12V battery as required by the appropriate test plan.

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© 2023 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
Voltage of terminal 40
Values between 40V and 50V are normal – If the voltage is between 0V and 12V, please check the 48V
battery.
[IDE12495]_Torques
- The specified torque indicates if the BSG is supposed to provide electrical power to the vehicle or not. The
engine control module determines if and how much torque the BSG is supposed to generate.
- The starter-alternator torque indicates if the BSG is actually producing electrical power when the engine
control module requires it to do so. If the BSG is working correctly, both torque levels should be similar
(within 5 Nm of each other).

If both torque values are 0, attempt to force the vehicle into providing electrical power from the
BSG by turning the steering wheel several times to both end stops and back. You can also activate
auxiliary system, like the HVAC blower to high, rear window heating, seat heaters to increase the
electrical load on the vehicle.
[VO]_operation_mode
current status of the BSG
When assessing the BSG, refer to the following table
Specified torque (in
Nm)

Starter-alternator torque (in Nm)

Operation_mode_actual

Recommendation

0

0

Standby

No charging
demand = do not
replace belt-driven
starter-alternator

-6.5

-1

TorqueControlled

Belt-driven starteralternator does not
charge and needs
to be replaced

-9.5

0

Inverter fault

Belt-driven starteralternator does not
charge and needs
to be replaced

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© 2023 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
-9.5

-9.5

TorqueControlled

Belt-driven starteralternator charging
= do not replace
belt-driven starteralternator

-3

-1

TorqueControlled

Belt-driven starteralternator charging
= do not replace
belt-driven starteralternator

If this TSB shows the BSG to work within specifications, further vehicle diagnostics is required to determine the
root cause of the customer complaint. This however is outside of the scope of this TSB.
SVM Update Instructions
1. Follow all instructions in TSB 2011732: 00 Software Version management (SVM), operating instructions.
2. Update the starter/generator control module, C23 (address word 00CC) using the SVM action code as listed in
the table below, if necessary:
Model

Old Hardware Old Hardware Old Software
Part Number Version
Part Number
(or lower)

A6, A7, Q7,
and Q8

New
Software
Version

SVM Code
Input

(or higher)
4N0903028

4N0903028
(H, J, M, and
N)

Old
Software
Version

H17

(F, G, H, J, M,
and N)

523

527

CCA001

Warranty
Claim Type:

• 110 up to 48 Months/50,000 Miles.
• G10 for CPO Covered Vehicles – Verify Owner.
• 1-GW for vehicles that fall under the Starter-Alternator Limited Warranty Extension.

Service Number:
Damage Code:

2726
Software Update: 0039 – if no part is replaced and only the update is required
Replace starter-alternator: 0040

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© 2023 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
Labor Operations:

Diagnostic Time:

Software Update (Includes checking for DTCs) 0151 0000
Only if update required

Time stated on
the diagnostic
protocol (Max
100 TU)

Check starter-alternator

2726 0199

10 TU

Replace starter-alternator (if required
according to this TSB)

2726 XXXX

See SRT with
associated
operations

GFF – (If no software update was performed)

0150 0000

Time stated on
the diagnostic
protocol (Max
100 TU)

Road test prior to the service procedure

No allowance

0 TU

Road test after the service procedure

No allowance

0 TU

As per TSB 2058831/9
Claim Comment:
All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures
Manual. Claims are subject to review or audit by Audi Warranty.

Additional Information
The following Technical Service Bulletin(s) will be necessary to complete this procedure:
• TSB 2011732: 00 Software Version Management (SVM), operating instructions.
• TSB 2067906: 27 48V Reference: diagnosis and system information
All part and service references provided in this TSB (2058831) are subject to change and/or removal. Always
check with your Parts Department and/or ETKA for the latest information and parts bulletins. Please check the
Repair Manual for fasteners, bolts, nuts, and screws that require replacement during the repair.
©2023 Audi of America, Inc. All rights reserved. The 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.

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© 2023 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.