2025 Audi Q5 / SQ5 Headlight Defect Warning TSB 2078182/1

Symptoms

Owners of affected 2025 Audi Q5 and SQ5 vehicles may observe a yellow warning message in the instrument cluster stating, "Left/right main beam headlight defective. See owner's manual." This message typically appears while driving. The warning lamp might disappear after cycling the ignition off and on, but it can reappear intermittently during subsequent drives. Importantly, despite the warning, there are no functional restrictions or performance issues with the main beam headlights themselves.

Fault Codes / DTCs

When diagnosing this condition, technicians will find the diagnostic trouble code (DTC) C12FC01 logged in the vehicle's system. This specific code, C12FC01, indicates an "LED channel 4, electrical fault" with symptom 139272. The fault is typically recorded in diagnostic address 0029, which corresponds to the Left light control unit, and/or diagnostic address 0039, which manages the Right light control unit.

Diagnosis / Trigger Conditions

The primary diagnostic step involves confirming the customer's complaint by reproducing the warning message in the instrument cluster. Technicians should also verify the presence of DTC C12FC01 within the Left light control (0029) and/or Right light control (0039) modules. It is crucial to note that no actual functional limitations of the main beams or additional main beams will be observed, reinforcing that the issue is software-related rather than a hardware failure. This helps confirm the 2025 Audi Q5 headlight defective warning is due to software.

Important Warnings

Audi has issued specific instructions for this condition under TSB 2078182/1 (PSS 94):

• "Explain to the customer that a solution is expected to be available by the end of the 2nd quarter of 2025 (subject to change) and that no repairs are necessary at this point." This means owners should not expect an immediate fix and that the warning does not indicate an urgent safety concern.
• "Do not replace any components for this condition since this will not resolve the customer's concern." This advises against unnecessary parts replacement, preventing potential costs and ensuring the correct, software-based solution is awaited.
• "This PSS may apply to vehicles still in the new model launch repair authorization period! For vehicles still in launch phase, create a TAC case per the repair authorization in addition to entering vehicle into the PSS Database. Reference this TSB in the TAC case." This instruction is primarily for dealers, highlighting the process for vehicles in their initial launch phase.

Repair Procedure Summary

The underlying cause of the "Left/Right main beam headlight defective" warning and DTC C12FC01 is a software issue. Audi plans to release a new ZDC software version to address this. This updated software will be available for the control units with diagnostic addresses 0029 (Left light control) and 0039 (Right light control). The new ZDC version is anticipated to be available from approximately the end of week 26/2025 onwards. Once released, the update will be installed in the corresponding control unit using standard software configuration procedures.

Owner Action

If you own a 2025 Audi Q5 or SQ5 and experience the "Left/Right main beam headlight defective" warning message or encounter DTC C12FC01, there is no immediate repair required. Audi advises against replacing any components, as this will not resolve the software-related issue. A permanent software solution is expected to be available by the end of the second quarter of 2025. You should discuss this with your authorized Audi dealer during your next service visit once the software update is released for the 2025 Audi Q5 headlight defective warning.

Source Citation

NHTSA ID: 11020363