2017-2021 Audi Models Hard Brake Pedal No-Start TSB 2055646/3

Revision History

This Technical Service Bulletin, 47 22 12 2055646/3, was initially published on July 17, 2019, as Revision 1. It was subsequently revised on February 18, 2021, as Revision 2, which included updates to the title, header (adding models), service instructions (adding Elsa location), and additional information (adding references). The current Revision 3, dated June 9, 2022, includes a revised warranty table. This bulletin supersedes Technical Service Bulletin Group 47 number 21-08, dated February 25, 2021.

Symptoms

Owners of affected 2017-2021 Audi models, including the 2021 Audi Q8, may notice a specific issue: after a short stationary period, the vehicle "sporadically does not start" and there is a "hard brake pedal concern." This means the brake pedal feels stiff and difficult to depress when attempting to start the engine.

Technical Background

The root cause of the 2021 Audi Q8 hard brake pedal and no-start condition is linked to the brake servo system. Dirt particles can accumulate in the non-return valve located within the vacuum hose for the brake servo. This contamination prevents the vacuum from being properly maintained within the brake servo when the vehicle is parked.

Normally, the brake servo should maintain a vacuum of 600 to 950 mbar. However, with a faulty non-return valve, the vacuum can drop by up to 400 mbar within 12 hours, depending on factors like the vehicle's parking position (e.g., on a slope) or user behavior. When the vacuum is insufficient, the usual brake force required to activate the brake light switch for start authorization is not met, leading to the no-start issue.

Repair Procedure Summary

To address the hard brake pedal and no-start condition described in TSB 47 22 12 2055646/3, technicians are instructed to replace the component identified as the "vacuum hose with non-return valve and pressure sensor – G608." This procedure must be performed according to the detailed instructions found in the Elsa Repair Manual, specifically within the "Brake System >> 47 Hydraulic Components >> Vacuum System" section.

Required Parts and Tools

For this repair, the primary part required is the "vacuum hose with non-return valve and pressure sensor." A quantity of one (01) of this part is needed. Additionally, any necessary fasteners, bolts, nuts, and screws should be replaced as needed per the repair manual. Technicians should always consult their Parts Department and/or ETKA for the latest information and part bulletins, and ETKA/ELSA for specific part numbers and quantities of fasteners.

Warranty Information

This repair is generally covered under warranty. The applicable Claim Type is 110 for vehicles up to 48 months or 50,000 miles. For Audi Certified Pre-Owned (CPO) vehicles, Claim Type G10 applies, requiring verification of the owner. The Service Number for this operation is 4777, and the Damage Code is 0010.

Labor operations and their associated time units (TU) include:

• Vacuum hose remove + reinstall: 4777 1950 (See SRT with associated operations)
• Brace remove + reinstall: 4086 1999 (50 TU, only if installed in the vehicle)
• Cowl panel trim remove + reinstall: 6644 19XX (See SRT with associated operations)

All warranty claims must be submitted in accordance with the Audi Warranty Policies and Procedures Manual and are subject to review or audit by Audi Warranty.

Important Warnings

If your vehicle is outside of any applicable warranty coverage, this Technical Service Bulletin is informational only. The repair costs in such cases would typically be the owner's responsibility.

Owner Action

If you experience a 2021 Audi Q8 hard brake pedal and no-start condition or any of the symptoms described in this TSB, it is recommended to contact an authorized Audi dealer. They can diagnose the issue and perform the necessary repair using the guidelines provided in TSB 47 22 12 2055646/3.

NHTSA ID: 10220676