2021-2023 Audi 48V System Warning P0CA700 U046900

Symptoms of an Audi 48V Warning

Audi has released Technical Service Bulletin 2058831/5, which supersedes an earlier bulletin (Group 27 number 22-41 dated March 2, 2022), to address concerns with the 48V electrical system. Owners of certain 2021-2023 Audi models equipped with this system may experience various issues. The most common symptom is an intermittent "48V vehicle electrical system warning" displayed in the instrument cluster. This Audi 48V warning can indicate underlying problems that may escalate if not addressed.

Additional customer-reported symptoms include:

• "The vehicle does not start."
• "The vehicle stalled."
• "The battery is dead."

These symptoms point to a potential malfunction within the 48V electrical system, impacting the vehicle's ability to start or operate reliably.

Fault Codes and Diagnosis

When diagnosing issues related to the 48V electrical system, technicians may find specific Diagnostic Trouble Codes (DTCs) stored in the vehicle's control modules. These codes help pinpoint the exact nature of the problem.

Diagnostic Trouble Codes (DTCs)

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

Trigger Conditions

For vehicles presenting with DTC U046900 in the ECM (J623), technicians will examine the expanded ambient conditions associated with this DTC. Specifically, they will look for the value of “Starter generator, actual mode 48V”. If this value is found to be “5”, it indicates a specific failure mode requiring a hardware replacement. If no value is displayed, further diagnostic feedback is required.

Important Warnings

Audi emphasizes the critical nature of addressing the "48V vehicle electrical system warning". If this warning, displayed in the instrument cluster, is ignored, the 12V system may drain. This can lead to severe consequences such as a complete vehicle stall or a no-start condition, leaving drivers stranded.

Repair Procedure Summary for Audi 48V Warning

Technical Service Bulletin 2058831/5 outlines the necessary steps to resolve the Audi 48V warning and associated DTCs. The repair typically involves either a software update or the replacement of the starter generator, depending on the diagnostic findings.

1. Software Update: The primary solution involves updating the software in the starter/generator control module (C29, address word 00CC). This update is crucial for correcting communication errors or operational inefficiencies within the 48V system. Technicians must follow the instructions detailed in TSB 2011732: 00 Software Version Management (SVM) for proper execution.
2. Starter Generator Replacement: If diagnostics reveal DTC U046900 and the “Starter generator, actual mode 48V” value in the expanded ambient conditions is “5”, the starter generator itself requires replacement. This indicates a hardware fault that cannot be resolved with a software update alone.

Required Parts and Codes

For repairs under TSB 2058831/5, specific part numbers and service codes are used:

• Starter/Generator Part Number: 4N0903028
• SVM Action Code: CCA001 (used for updating the starter/generator control module C29)
• Service Number: 2726
• Damage Codes:
  • 0039: For software updates where no part is replaced.
  • 0040: For replacement of the starter-alternator.
• Labor Operations:
  • 0151 0000: For software updates, including DTC checks.
  • 2726 XXXX: For replacing the starter-alternator when the “Starter generator, actual mode 48V” value is 5.

Owner Action

If you experience a "48V vehicle electrical system warning" or any of the related symptoms like your Audi not starting or stalling, it is recommended to contact an authorized Audi dealership. Provide them with the symptoms you've observed. The dealership technicians will perform the necessary diagnostics, which may include checking for DTCs P0CA700 and U046900, and apply the appropriate software update or replace the starter generator as outlined in Technical Service Bulletin 2058831/5.

This repair is typically covered under Audi's new vehicle limited warranty (up to 48 months/50,000 miles) or Certified Pre-Owned (CPO) warranty. If your vehicle is outside of these warranty periods, the bulletin serves as informational guidance.

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Source: NHTSA ID: 10222114