2021 Audi A6/A7/S6/S7/S8 48V Electrical System Warning TSB

Audi has issued Technical Service Bulletin (TSB) 27 21 37 2058831/2 to address an intermittent "48V vehicle electrical system warning" displayed in the instrument cluster of certain 2021 Audi models. This TSB specifically applies to A6, S6, A7, S7, and S8 vehicles equipped with the 48V Mild Hybrid Electric Vehicle (MHEV) system.

The TSB, which supersedes an earlier bulletin (20-35 dated March 10, 2020), provides a software update solution for diagnostic trouble codes (DTCs) P0CA700 and U046900. Owners experiencing a 2021 Audi A6 48V electrical system warning should be aware of this update.

Symptoms

Owners may observe an intermittent warning message related to the 48V vehicle electrical system appearing in their vehicle's instrument cluster. This warning indicates a potential issue with the mild hybrid system.

Fault Codes / DTCs

Technicians diagnosing this issue may find one or both of the following diagnostic trouble codes stored in the vehicle's control modules:

Code	Description	Module	Address Word
P0CA700	hybrid battery discharge current too high static or sporadic	Battery 48V control module (J1120)	0021
U046900	invalid data received from starter/generator control module	Engine control module (ECM) (J623)	0001

Technical Background

Audi has determined that the root cause of these symptoms and DTCs is a software anomaly within the starter/generator control module, identified as C29 (address word 00CC). A software update is necessary to correct this condition and prevent the 2021 Audi A6 48V electrical system warning from appearing.

Repair Procedure Summary

To resolve the issue, a software update for the starter/generator control module (C29) is required. The repair involves following the instructions outlined in TSB 2011732, titled "00 Software Version Management (SVM), operating instructions." The update is performed using a specific SVM action code.

The process includes updating the starter/generator control module, C29, to the new software version. The old hardware part number 4N0903028 (versions H, J, M, N) and old hardware version H17 (versions F, G, H, J, M, N) with old software version 523 will be updated to new software version 527 using SVM Code Input CCA001.

Required Tools or Parts

No specific physical parts are required for this repair, as it is a software update. However, the procedure necessitates access to Audi's diagnostic tools and the SVM system. The new software version is 527, and the SVM Code Input for the update is CCA001.

Warranty Information

This service is covered under Audi's New Vehicle Limited Warranty for up to 48 months or 50,000 miles, whichever comes first. For Audi Certified Pre-Owned (CPO) vehicles, the claim type G10 applies, subject to owner verification. If the vehicle is outside of any applicable warranty, this Technical Service Bulletin serves as informational guidance only, meaning the repair cost would be the owner's responsibility.

Important Warnings

Owners should be aware that if their vehicle is no longer under warranty, this Technical Service Bulletin is for informational purposes only. This implies that the cost of the software update, if performed outside of warranty coverage, would typically be borne by the vehicle owner. Always confirm warranty eligibility with an authorized Audi dealer.

NHTSA ID: 10190275