2021 Audi Q5 Rear Light Switch Fault B146C29 TSB

Audi has issued Technical Service Bulletin (TSB) 94 21 47 2050234/5, dated September 22, 2021, to address a condition where the rear lights on certain Audi Q5 models do not switch correctly. This TSB, which supersedes Group 94 number 18-96 dated January 30, 2018, specifically targets the Audi Q5 rear light switch fault B146C29 and provides detailed diagnostic and repair instructions.

Symptoms

Owners of affected 2021 Audi Q5 vehicles may notice several issues related to the rear lighting system. The most common symptom is "The brake light warning is on in the instrument cluster."

Another key indicator of an Audi Q5 rear light switch fault B146C29 is that "When the rear lid is closed, the lights in the rear bumper do not switch over to the main lights on the rear lid." Despite these warnings, owners often find that "All of the rear light bulbs are fully functional. None are found to be faulty or incorrect."

Fault Codes / DTCs

When diagnosing this issue, technicians may find a specific Diagnostic Trouble Code (DTC) stored in the comfort system central control module, J393 (address 0046). The primary DTC associated with the Audi Q5 rear light switch fault B146C29 is:

• DTC B146C29: "Rear lid -closed- sensor implausible signal"

Technical Background

The rear lighting system in the Audi Q5 is designed to switch between the rear lid lights and the bumper lights depending on whether the rear lid is open or closed. This change-over is managed by two micro switches located under the loading sill cover on the rear cross panel, secured to the striker for the rear lid lock.

The TSB identifies two main reasons why these micro switches might malfunction:

1. Broken Paddle: The paddle on one or both micro switches can break due to improper adjustment of the rear hatch or the striker during vehicle production.
2. Debris Obstruction: Dirt or debris can block one or both paddles on the micro switches, preventing them from operating correctly. Figure 2 in the original document illustrates debris trapped in the rear lid closed sensor.

Production Improvements

Audi has implemented production changes to mitigate this issue. The adjustment of the rear hatch has been optimized, and an improved rear lid closed sensor assembly, featuring an additional enclosure, is now installed. This new design enhances debris resistance for the switches, though it cannot entirely eliminate the possibility of debris ingress.

Repair Procedure Summary

Addressing the rear light switch fault involves a series of diagnostic and repair steps:

1. Sensor Replacement: If the rear lid closed sensor is found to be physically broken, it should be replaced. The TSB includes an image (Figure 1) showing the rear lid closed sensor.
2. Debris Removal: If debris is obstructing the proper activation or deactivation of the switch, technicians should manually activate the switch paddles and remove the debris. Using compressed air is recommended for effective cleaning.
3. Measuring Value Check: After cleaning or initial replacement, the measuring values for the G525 and G526 switches should be checked. If the malfunction persists, the rear lid closed sensor should be replaced with the improved version, which includes the protective enclosure.

Required Parts and Tools

For repairs related to this TSB, the following parts may be required:

• Rear Lid Closed Sensor: Quantity 01 (Refer to ETKA for specific part numbers).
• Fasteners, Bolts, Nuts, and Screws: As needed (Refer to ETKA/ELSA for specific requirements).

Warranty Information

Warranty claims for this repair are covered under specific conditions:

• Standard Warranty: Up to 48 months or 50,000 miles.
• CPO Vehicles: G10 claim type for Certified Pre-Owned (CPO) vehicles, requiring owner verification.
• Out of Warranty: If the vehicle is outside of any applicable warranty, this Technical Service Bulletin is for informational purposes only, meaning the repair may not be covered by Audi.

Service Number: 9661 Damage Code: 0015

Labor Operations:

• Lock carrier cover remove + reinstall: 7039 1900
• Rear Lid Closed Sensor G525/G526 replacement: 9661 1950
• Rear Lid Closed Sensor G525/G526 - repair: 9661 1999 (30 TU)

Diagnostic Time: GFF 0150 0000 (20 TU)

Road tests performed before or after the service procedure are not allowed for warranty claims under this bulletin.

Source: NHTSA ID 10201551