2018-2023 Audi 48V Electrical System Warning TSB

Revision History

This Technical Service Bulletin, 2058831/6, dated March 23, 2023, supersedes Group 27 number 22-45, which was dated September 27, 2022. Key revisions include updates to the header, customer statement, diagnosis and service procedures, and warranty information. Earlier revisions also added model years 2022 and 2023, and updated symptom and damage codes.

Symptoms

Owners of 2018-2023 Audi vehicles may observe a "Electrical system: fault. See owner's manual" message displayed on the instrument cluster. Additionally, a "yellow or red battery warning symbol" may illuminate, indicating a potential issue with the 48V electrical system.

Fault Codes / DTCs

When the Audi 48V electrical system warning appears, technicians may find one or more of the following Diagnostic Trouble Codes (DTCs) stored in the vehicle's control modules:

Code	Description	Module	Address Word
P0CA700	Hybrid battery discharge current too high	Battery management 2 (Battery 48V) control module	J1120 (0021)
U046900	Invalid data received from starter/generator control module (Symptom 36564)	ECM	J623 (0001)
U046900	Invalid data received from starter/generator control module (Symptom 36564)	Gateway	J533 (0019)

Technical Background

The Belt Starter Generator (BSG), together with the vehicle's 48V system, is an intelligent vehicle system that provides electrical power as needed. Traditional diagnostic methods for alternators are not suitable for this system, as the BSG's output power is regulated based on current vehicle requirements. The Audi 48V electrical system warning can stem from either a software-related issue or a hardware malfunction within the BSG system. For more detailed information, technicians can refer to TSB 2067906: 27 48V Reference: diagnosis and system information.

Diagnosis and Trigger Conditions

Diagnosis for the Audi 48V electrical system warning involves checking for specific conditions and software versions. If the "Starter generator, actual mode 48V" value is not displayed or is not equal to 5, the Belt Starter Generator (BSG) software version (address word 00CC) should be checked. If the software is older than version SW 0527, an update is required.

If the BSG software is already at or newer than SW 0527, or if it has been updated, further diagnostic steps are necessary. These include selecting the "00CC - Starter Generator" measurement values in ODIS and monitoring specific parameters such as [IDE12494]_Voltages, [IDE12495]_Torques, and [VO]_operation_mode while the engine idles in park. The voltage of terminal 87 should be between 11.6V and 15V; if below 11.6V, the 12V battery may need recharging or replacement. The voltage of terminal 40 should be between 40V and 50V; if between 0V and 12V, the 48V battery should be checked.

Important Warnings

If both the specified torque and starter-alternator torque values are 0 during diagnosis, technicians are advised to increase the electrical load on the vehicle. This can be done by turning the steering wheel to both end stops multiple times or activating auxiliary systems like the HVAC blower on high, rear window heating, or seat heaters. This action helps to force the vehicle into providing electrical power from the BSG.

When assessing the BSG's operation mode, refer to the following recommendations:

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 starter-alternator does not charge and needs to be replaced
-9.5	0	Inverter fault	Belt-driven starter-alternator does not charge and needs to be replaced
-9.5	-9.5	TorqueControlled	Belt-driven starter-alternator charging = do not replace
-3	-1	TorqueControlled	Belt-driven starter-alternator charging = do not replace

Repair Procedure Summary

The primary repair for the Audi 48V electrical system warning involves a software update for the starter/generator control module (C23, address word 00CC). This update is performed using the SVM update instructions detailed in TSB 2011732: 00 Software Version management (SVM), operating instructions. The specific SVM action code for this update is CCA001.

For models A6, A7, Q7, and Q8, the old hardware part number is 4N0903028 (revisions H, J, M, and N) with an old hardware version H17. The old software version is 523, and the new software version is 527. The SVM code input for this update is CCA001.

If the software update does not resolve the issue, or if initial diagnostics indicate a hardware fault, further investigation of the Belt Starter Generator is required. This involves checking the 12V and 48V battery voltages, ensuring they are within normal ranges. If the voltage is too low, the battery may need recharging or replacement. The torque values from the BSG are also compared to determine if the unit is charging correctly or if it has an inverter fault, which would necessitate replacement of the belt-driven starter-alternator.

Required Tools or Parts

Technicians will need access to the ODIS diagnostic system to perform the necessary checks and software updates. The SVM action code CCA001 is used for updating the starter/generator control module, C23. The target software update is from version 523 to 527. The relevant hardware part number for the BSG is 4N0903028 (various revisions).

Warranty Information

Warranty claims for this issue must adhere to the Audi Warranty Policies and Procedures Manual. The Service Number for this procedure is 2726. Applicable claim types include 110 (up to 48 months/50,000 miles), G10 (for CPO Covered Vehicles - Verify Owner), and 1-GW (for vehicles under the Starter-Alternator Limited Warranty Extension).

Damage codes are 0039 for software updates (if no part is replaced) and 0040 for replacing the starter-alternator. Labor operations include 0151 0000 for software updates (including checking for DTCs) and 2726 0199 for checking the starter-alternator. If a starter-alternator replacement is required, labor operation 2726 XXXX applies. Diagnostic time is 0150 0000 (if no software update was performed), with no allowance for road tests before or after the service procedure.

Owner Action

If you experience the "Electrical system: fault. See owner's manual" message or a "yellow or red battery warning symbol" in your 2018-2023 Audi, it is recommended to contact your authorized Audi dealer. They have the necessary diagnostic tools and software updates (TSB 2058831/6) to properly diagnose and address the underlying issue with the 48V electrical system and Belt Starter Generator.

NHTSA ID: 10233377