2021-2023 Audi Q8 Electrical System Fault P0AA100 TSB

Owners of certain 2021-2023 Audi Q8 vehicles and other Audi models may encounter instrument cluster warnings such as "Electrical system: fault. Please contact workshop" or "Drive system: fault. Please contact workshop." These messages are often accompanied by the diagnostic trouble code (DTC) P0AA100, indicating a Hybrid/EV Battery Positive Contactor Circuit Stuck Closed fault. This bulletin, Audi TSB 2070813/1, addresses this specific Audi Q8 electrical system fault P0AA100.

Symptoms

If your vehicle is affected by this issue, you may observe the following messages displayed on the instrument cluster:

• "Electrical system: fault. Please contact workshop"
• "Drive system: fault. Please contact workshop"

These warnings indicate a problem within the vehicle's electrical or drive system, specifically related to the 48V battery.

Fault Codes / DTCs

When diagnosing this condition, a technician may find the following diagnostic trouble code stored in the battery management 2 (48V battery) control module (address word 0021):

• DTC P0AA100: Hybrid/EV Battery Positive Contactor Circuit Stuck Closed

Diagnosis / Trigger Conditions

This Audi Q8 electrical system fault P0AA100 is a software-related issue affecting the 48V battery in conjunction with the active roll stabilization system (PR number 2MQ). The DTC P0AA100 can be stored when the engine is turned on after the 48V system has been deactivated for more than 16 minutes. In vehicles with active roll stabilization, the 48V system remains active even when the engine is not running, causing capacitors on the 48V system to charge when the ignition is on.

The fault can be reproduced under specific conditions:

1. The vehicle is switched off and remains off for over 16 minutes.
2. The vehicle is then unlocked and entered, which activates the roll stabilization and the 48V system.
3. The customer subsequently leaves the vehicle again.
4. The customer returns within 16 minutes and switches on the ignition.
5. At this point, DTC P0AA100 is set.

Even if voltage is present before and after an open relay during diagnosis (due to charged capacitors), this condition is logged as an event memory entry for P0AA100.

Repair Procedure Summary

Audi's solution for this condition is a software update for the battery management 2 (48V battery) control module. This update resolves the underlying software issue that causes the Audi Q8 electrical system fault P0AA100.

Technicians will perform the following steps:

1. Preparation: Ensure the diagnostic system is configured correctly. It is crucial to use DoIP (Diagnostic over Internet Protocol) when flashing control modules via ODIS in supported vehicles. To activate DoIP, technicians must navigate to Administration>>General>>GFF Process>>DoIP communication>>Only allow DoIP communication. This setting will automatically reset once the diagnostic session concludes. A red LED on the VAS 6154(A) interface indicates that DoIP is active.
2. Software Version Management (SVM): Follow the instructions detailed in TSB 2011732: 00 Software Version Management (SVM), operating instructions.
3. Module Update: Update the battery management 2 (48V Battery) control module (address word 0021) using the SVM action code 21A003. This will install the latest software version to correct the fault.

Required Software/Parts

The software update involves replacing older software versions with newer ones. The relevant software part numbers are:

Model	Old Software Part Number	Old Software Version	New Software Part Number	New Software Version
A6/A7/A8/Q7/Q8	4N0.915.105.B	0108, 0109	4N0.915.105.E	0113
A6/A7/A8/Q7/Q8	4N0.915.105.D	0206, 0207	4N0.915.105.F	0211

Important Warnings

• DoIP Activation: When flashing a control module via ODIS, always use DoIP in supported vehicles. Ensure DoIP is activated by following the specific menu path: Administration>>General>>GFF Process>>DoIP communication>>Only allow DoIP communication. This setting will reset after the diagnostic session ends. A red LED on the VAS 6154(A) indicates active DoIP.
• Warranty: This Technical Service Bulletin is informational only if your vehicle is outside of its warranty period. Warranty claims are subject to review by Audi Warranty and must adhere to the Audi Warranty Policies and Procedures Manual.

Owner Action

If your 2021-2023 Audi Q8 or other affected Audi model is displaying the