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AUDI Q3 – ADAPTIVE LIGHT FAULTY AFTER OBD11/OBDELEVEN: CAUSES, DIAGNOSIS, SOLUTIONS (2025)

Updated August 2025 — edited by Gianni Tritella.

After certain OBDeleven/OBD11 coding operations (e.g., activating automatic high beams / Light Assist ), the Audi Q3 may display the "Adaptive Light: fault" warning or other warning lights related to the headlight alignment. In this guide, I explain why this happens , how to safely diagnose the issue, and the repair and calibration procedures that resolve the issue in most cases in the workshop.

When it happens and why

In most cases, the warning appears after adjustments to the 09 (Body/BCM) and/or A5 (Front Sensor Driver Assist) control unit without having performed the headlight/AFS calibration in 55 – Headlight Range . Sometimes the coding enables functions not supported by the installed hardware (absence of a windshield camera or trim sensors), generating DTCs and limitations.

• AFS “Basic Setting” failure after coding or battery disconnection.
• Inconsistent parameters between 09↔A5↔55 (CAN messages requested but not present).
• Partial retrofit : Light Assist is enabled without camera/related PR parameters.

🔎 Step-by-step diagnosis (workshop method)

1. Complete Backup & Scan with OBDeleven:
   • Save Long Coding and Adaptation by 09, A5, 55 .
   • Read DTCs and freeze frames to understand when they are triggered.
2. Hardware Check :
   • Is there a windshield camera? Are the axle level sensors connected?
   • Check PR-code (e.g. 8G1/8G4 for Light Assist) in the equipment tab.
3. Power and network control :
   • Battery voltage > 12.4 V; no CAN gateway error.
   • Dry, oxide-free headlight and level sensor connectors.
4. Module alignment :
   • In 55 – Headlight Range run Basic Settings “AFS calibration/headlight alignment”.
   • In A5 check camera calibration status (if present).
5. Road test :
   • DTC reset → road test; perform a full left-right turn at low speed.

🛠️ Quick reset (keeping automatic high beams on)

If you want to keep the HBA active:

1. OBDeleven Change History on 09 and A5 : Only undoes the adaptations that generated the DTCs (compare notes and timestamps).
2. 55 – Headlight Range :
   • Perform Reset Adaptations → Basic Settings headlight calibration/aiming (flat floor, correct tire pressure, standard load).
3. Clear DTCs in 09, A5, 55 → road test with full lock.

♻️ Complete restoration to stock

1. Restore Long Coding and Adaptation of 09 and A5 from History .
2. Perform calibration in 55 as above, then clear DTC.
3. If the error persists, disconnect the battery (3–5 minutes), reconnect, and rescan. As a last resort, update the OEM software or check with a service network.

✅ Correct activation of automatic high beams (guidelines)

To enable Light Assist on prepared vehicles:

• Make sure the hardware is present (windshield camera and wiring) and the function is expected by the chassis.
• Make the minimum adjustments required in 09 and A5 (following a reliable guide for your MY ).
• Always finish with Basic Settings AFS at 55 and a short night road test to validate.

Note: Enabling unsupported features may result in permanent limitations until reset and calibrated.

📟 Typical errors and what they mean (indicative)

• AFS/Headlight Range – missing calibration : control unit 55 requests Basic Setting .
• Missing CAN messages 09↔A5↔55 : Coding requiring signals from a module that is not present.
• Camera not calibrated : after windshield replacement or newly enabled HBA; camera calibration required.

🛡 Prevention and best practices

• Always first: Run full scan and backup of 09, A5, 55.
• Stable power supply: Use 12V maintainer during long encoding.
• One edit at a time and clear notes on what you do.
• AFS calibration after any work involving headlights, suspension or battery.
• Hardware before software: Do not activate functions if sensors/cameras are missing.

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❓ FAQ – Frequently Asked Questions

I turned on the automatic high beams and now I see "Adaptive Light: fault." Should I go back?

Not necessarily. Often it is sufficient to perform the AFS calibration in ECU 55 – Headlight Range and clear the DTCs. If the hardware is not present or the required CAN messages are missing, then it is best to restore the adaptations in 09/A5 from the History .

Which control units should I check first?

09 (Body/BCM) , A5 (Front Sensor Driver Assist) and 55 (Headlight Range/AFS) . Make backups of Long Coding and Adaptation , read the DTCs and proceed with calibration in 55.

Do you need a windshield camera for Light Assist?

Yes, on models that require it. Enabling HBA without a camera or calibration leads to errors and limitations .

Can the L↔R steering cycle really help?

Yes, after calibration/zeroing, some systems require a brief lock-to-lock to realign the references. This must be done safely at low speed.

When is it best to contact a specialized center?

If persistent errors appear in 55/A5 after calibration, if there has been a headlight/camera retrofit , or if you suspect a hardware failure (level sensor, wiring, LED/Matrix headlights).

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