2017-2025 Audi Q5/Q7 Taillight Switching Issue B146C29

Owners of certain 2017-2025 Audi Q5, Q5 Sportback, and Q7 models may encounter a functional issue where the vehicle's rear lid taillights do not switch correctly or remain illuminated constantly. This problem is addressed by Audi Technical Service Bulletin (TSB) 2070964/3, which outlines the cause and a simple diagnostic and repair procedure.

The TSB, with its latest revision released on September 12, 2025, provides guidance for technicians on how to resolve this specific lighting malfunction. The primary cause for this Audi Q7 taillight issue B146C29 is often environmental factors affecting key components.

TSB Revision History

Technical Service Bulletin 2070964/3 has undergone several revisions to refine its guidance:

• Revision 3 (Latest): Updated the title, header to include additional model years, and revised the condition description.
• Revision 2 (April 11, 2024): Revised the header to remove invalid sales types, specifically MY25 Q5 and MY24 Q7 models.
• Revision 1 (November 17, 2023): Initial publication of the bulletin.

Symptoms

Owners may observe the following issues related to the rear taillights, which are also reported as customer complaints:

• The taillights do not switch correctly when the rear lid is opened or closed.
• The taillights located in the bumper remain lit constantly, even when they should be off.
• Other related complaints include dimensional inaccuracies or incorrect play/fit of the rear lid, contamination (dirty brake light lens, multifunction toolbar, rear bulkhead), and functionality issues where parking lamps cannot be switched off/deactivated or on/activated.

These symptoms indicate a malfunction in the rear lid's sensing mechanism, which controls the taillight operation.

Fault Codes / DTCs

When diagnosing this issue, technicians may find a specific diagnostic trouble code (DTC) logged in the event memory of the convenience control unit (diagnostic address 0046).

Code	Description	Module
B146C29	Rear Lid Closed Sensor - Implausible signal	Convenience Control Unit

This DTC directly points to an unreliable signal from the rear lid closed sensor, which is central to the Audi Q7 taillight issue B146C29.

Technical Background

The root cause of the taillight switching malfunction is typically the presence of foreign bodies in the area of the rear lid's rotary latch or the rear lid sensor. Coarse dirt, small stones, or other loose debris can interfere with the proper operation of these components, leading to an implausible signal from the rear lid closed sensor.

Repair Procedure Summary

Audi's service procedure for addressing the Audi Q7 taillight issue B146C29 involves a straightforward inspection and cleaning process:

1. Inspect the Rotary Latch Area: Technicians should first check the area of the rotary latch for any coarse dirt, such as stones or other loose foreign bodies. Figures 1 and 2 in the TSB visually demonstrate examples of dirt and debris interfering with the rear lid sensor's operation.
2. Remove Debris: Carefully remove any coarse dirt, stones, or other loose foreign bodies found from the area of the latch or the rear lid sensor. After cleaning, recheck whether the taillights switch correctly.
3. Further Diagnosis (If Needed): If the issue persists after cleaning, technicians are instructed to check the measured value block in the convenience control unit (diagnostic address 0046) to verify proper sensor function. Any other required repair work should then be performed.

Important Warranty Information

Audi explicitly states that claims for replaced parts related to this issue will not be reimbursed. This damage is considered to be due to "outside influence" and is therefore not covered by any standard Audi Warranty. Owners should be aware that the cost of diagnosis and repair, particularly if it involves cleaning debris, may not be covered.

Owner Action

If you are experiencing the symptoms described, such as your taillights not switching correctly or staying on constantly, you can first inspect the area around your rear lid's rotary latch and sensor for visible dirt or debris. Carefully removing any obstructions might resolve the Audi Q7 taillight issue B146C29.

If the problem persists, it is recommended to contact an authorized Audi service center for diagnosis. Be prepared that repairs related to external debris may not be covered under warranty.

NHTSA ID: 10255308