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Technical Service Bulletin Transaction No.: 2058831/18
27 48V vehicle electrical system warning, DTC U046900 stored in the ECM Release date: Apr 30, 2026
Condition
| modes) | Year's) _| VIN Range Vehicle Specific Equipment
A8 and Q8 2019 - 2026
A6, and A7 2019 - 2025
With PR Code:
A6 allroad, and Q7 | 2020 — 2026 All
9G8
A8 e quattro 2020 - 2021
REVISION HISTORY
revision [ote _[rupose
18 Revised header (Added model years)
Revised Condition (Added model table)
Revised Warranty (Updated labor operations)
07/30/2025 | Revised Service (Updated information on repair)
03/04/2025 | Revised Additional information (Updated reference TSB)
Customer states:
+ The message “Electrical system: malfunction! Please contact Service” is displayed on the instrument cluster
(Figure 1), in addition the battery symbol lights up in yellow or red.
+ Yellow warning lamp related to the electrical system shown in the instrument cluster during driving.
=
|
|
\ | ii |
) Electrical system:
]/ malfunction! Please || 4
A \
// contact Service \

Figure 1. Cluster Warning Message.

Workshop findings:

The following DTC is stored in the ECM, J623 (address word 0001):

+ DTC U046900: Invalid data received from starter/generator control module (symptom 36564).

Take note of the symptom 36564, if this is not present this TSB does not apply.

Technical Background
1. Hardware issue with belt-driven starter-alternator (diagnostic address 00CC).

2. Functional software issue with belt-driven starter-alternator (diagnostic address 00CC).

Production Solution

Not Applicable.

Service

If the complaint described above can be reproduced, then proceed as follows:

+ Check if ODIS S software is the latest version, update if necessary.

While diagnosing the 48V system ensure the 48V and 12V battery are charged properly prior to following
the procedure. Also, TSB 2067906: 27 48V Reference: Charging 48V Battery with 12V Charger DTC
P0A7D00 / POB2900 must be observed, otherwise a specific diagnosis is not possible.

In the diagnosis (not self-diagnosis), select the function test “C29 — read_delete and attach to test plan.
Note: Answer the question that appears in the test plan - “Are you running this program based on an
instruction in a TPI?” — with YES.

ODIS path for A4/A5/Q7:

+ Body
+ Electrical system
* 01 - On Board Diagnostic capable systems
+ CC - starter-alternator -C29
+ CC - Functions
+ 00CC - Check/erase event memory entry

ODIS path for AG/A7/A8/Q8:

+ Diagnostic capable system

+ 00CC - starter alternator -C29

+ OOCC - Functions

+ 00CC — Check/erase event memory entry

If the following DTC is shown in ODIS, replace the starter-alternator according to ETKA and check whether the
complaint has been resolved:

+ B200096 - Faulty control module (active/static or passive/intermittent).

If the DTC is not stored in the test plan, then the generator is not faulty and replacing parts will not fix the
problem.

For invoicing under warranty, the above-mentioned DTC “B200096 - control unit defective” must be present
in the ODIS test plan “C29 — Read_Delete DTC” in the diagnostic log.
Important information on repair (replacement of belt-driven starter-alternator): risk of damage to radiator
outlet coolant temperature sender G83 (future follow-up complaints may arise months later) or
communication problems with new belt-driven starter-alternator due to coolant entering the electrical
connector. Coolant entering the electrical connector can lead to delayed subsequent corrosion damage to
the electrical contacts.

Seal the electrical connectors on the coolant temperature sender, the mating connector and the signal
connector to belt-driven starter-alternator with leak-tight connector -T40348- or suitable workshop
materials. Visually inspect components for moisture before assembly and clean electrical contacts if
necessary.

Note on working aid for the required function checks in the event that the belt-driven starter-alternator
needs replacing:
The file “Working_aid_for_necessary_functional_tests” which is attached to this TSB contains the function
checks in ODIS which are required for this workshop visit.
Warranty

In the exceptional case described here, contrary to the general rules specified in the warranty handbook, proof of
the inspection and servicing work carried out so far is not required for billing for the fault described.

Nevertheless, when returning the vehicle you should inform the customer of the importance of adhering to the
maintenance and servicing requirements and the service intervals.

Claim Type: + Ifthe vehicle is outside of any warranty, this Technical Service Bulletin is

informational only.

Damage Code: 0040
Labor Operations: If Starter-alternator is not replaced:
GFF (only if starter-alternator is not replaced) 0150 0010 |See SRT with
associated operations
GFF (only if starter-alternator is not replaced) 0150 0060 | Time stated on the
diagnostic protocol
Check high-voltage system (48V) 93100199 |80 TU
Service high-voltage system (48V) 93104199 | Please bill according to
the time required
OR
If Starter-alternator is replaced:
Replace starter-alternator (If required according to |2726 19xx/|See SRT with
this TSB) 2726 55xx associated operations
12NV battery Charge (if starter-alternator requires 2706 8950 | See SRT with
replacement) associated operations
GFF (If starter-alternator requires replacement) 0150 0060 | Time stated on the
diagnostic protocol
Check high-voltage system (48V) 93100199 |80 TU
Service high-voltage system (48V) 9310 4199 | Please bill according to
the time required
Claim Comment: As per TSB 2058831/18
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.
Please note the information on predecessors and items that are included and excluded in the repair operations, as
well as any associated tasks.
Required Parts and Tools
Exchange parts must be installed if available in the exchange program. If a new part is installed instead of an
exchange part in justified cases, the reason for this must be given in the comment field in SAGA/2.
Additional Information
The following Technical Service Bulletin will be necessary to complete this procedure:
+ TSB 2067906: 27 48V Reference: Charging 48V Battery with 12V Charger DTC POA7DO0 / POB2900.
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.
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