2021 Audi Hard Brake Pedal While Starting TSB

Symptoms

Owners of certain 2021 Audi models may experience a "hard brake pedal while attempting to start the vehicle" after a short stationary period. This condition can also lead to the vehicle sporadically failing to start. This "hard brake pedal concern" indicates an issue with the brake system's vacuum.

Technical Background

This issue stems from dirt particles accumulating in the non-return valve located within the vacuum hose for the brake servo. This contamination prevents the brake servo from maintaining sufficient vacuum when the vehicle is parked. Normally, the brake system's vacuum ranges from 600 to 950 mbar. However, with this fault, the vacuum can drop by up to 400 mbar within 12 hours, depending on factors like parking position (e.g., on a slope) or user behavior. When starting the vehicle, the reduced vacuum means there isn't enough brake force to activate the brake light switch, which is necessary for start authorization.

Repair Procedure Summary

To resolve the "2021 Audi hard brake pedal start" issue, technicians should replace the "vacuum hose with non-return valve and pressure sensor G608." This repair must be performed according to the detailed instructions found in the Elsa Repair Manual, specifically under Elsa >> Brake System >> 47 Hydraulic Components >> Vacuum System.

The repair process involves several labor operations, including:

• Removing and reinstalling the vacuum hose.
• Removing and reinstalling the cowl panel trim to access the affected components.

Required Parts and Tools

Technicians will need the following parts to complete the repair:

• One (01) vacuum hose with non-return valve and pressure sensor (Part Number: See ETKA).
• Necessary fasteners, bolts, nuts, and screws as required by the repair manual (Part Number: See ETKA/ELSA).

Always consult the Parts Department and/or ETKA for the latest information and specific part numbers.

Warranty Information

This Technical Service Bulletin (TSB) 47 21 08 2055646/2 outlines the warranty coverage for this repair:

• Claim Type: 110, applicable for vehicles up to 48 months or 50,000 miles.
• CPO Covered Vehicles: G10 claim type, requiring owner verification.
• Service Number: 4777
• Damage Code: 0010
• Labor Operations: Specific labor operation codes are 4777 1950 for vacuum hose replacement and 6644 19XX for cowl panel trim removal and reinstallation.
• Diagnostic Time: GFF, with no allowance (0 TU) for diagnostic or road test time prior to the service procedure.

Important Notes for Owners

If your vehicle is outside of its warranty period, this Technical Service Bulletin is for informational purposes only. You may be responsible for the cost of the repair.

Owner Action

If you are experiencing a "2021 Audi hard brake pedal start" or a sporadic no-start condition, contact your authorized Audi dealership. Describe the symptoms you are experiencing, and mention Technical Service Bulletin 47 21 08 2055646/2. The dealership can diagnose the issue and perform the necessary repair, which involves replacing the vacuum hose with the non-return valve and pressure sensor.

Source: NHTSA ID: 10187578