2021-2023 Audi Hard Brake Pedal While Starting TSB

Symptoms

Owners of affected 2021-2023 Audi vehicles 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 that when you attempt to start your car, the brake pedal feels unusually stiff, and the engine may not engage as expected. This "Audi hard brake pedal starting" issue can be intermittent.

Technical Background

The root cause of the "Audi hard brake pedal starting" problem lies within the brake system's vacuum circuit. Dirt particles can accumulate in the non-return valve located in the vacuum hose for the brake servo. This contamination prevents the vacuum in the brake servo from being maintained properly when the vehicle is parked.

Under normal conditions, a vacuum pressure of 600 to 950 millibars (mbar) is expected. However, with a compromised non-return valve, the vacuum can drop by up to 400 mbar within 12 hours, depending on factors like parking position or user behavior. When starting the vehicle, insufficient brake force due to this vacuum loss can prevent the brake light switch from authorizing ignition, leading to the hard brake pedal and no-start condition.

Diagnosis and Repair Procedure

Audi Technical Service Bulletin 2055646/4 outlines the steps technicians should follow to diagnose and repair this issue. The procedure involves a thorough inspection and potential replacement of components:

1. Component Inspection: Technicians will check the vacuum hose, sensor G608, connectors, seals, and other valves for any signs of damage.
2. Leak Detection: A detailed check for leaks will be performed according to the procedures outlined in the Elsa repair manual, specifically under "Brake System >> 47 Hydraulic Components >> Vacuum System."
3. Vacuum Hose Examination: The vacuum hose and its connection points to check valves will be inspected for small cracks or other damage.
4. Documentation: If any damage, cracks, or leaks are identified, photographic evidence will be taken and uploaded to the DOC-IT system.
5. Component Replacement: Any necessary components found to be damaged or leaking will be replaced following the guidelines in the Elsa Repair Manual, "Brake System >> 47 Hydraulic Components >> Vacuum System."

Required Parts and Tools

For this repair, specific parts are required, and their exact numbers should be confirmed using the ETKA parts catalog:

• Vacuum hose with non-return valve and pressure sensor: One unit is required. The specific part number should be referenced in ETKA.
• Fasteners, Bolts, Nuts, and Screws: As needed for the repair, these should also be sourced via ETKA or Elsa.

Warranty Information

This repair, identified by Service Number 4777 and Damage Code 0010, is typically covered under Audi's warranty programs:

• Standard Warranty: Covered for up to 48 months or 50,000 miles under Claim Type 110.
• CPO Vehicles: Covered for Certified Pre-Owned (CPO) vehicles under Claim Type G10, subject to owner verification.

Labor operations associated with this repair include "Vacuum hose remove + reinstall" (4777 1950), "Brace remove + reinstall" (4086 1999 if applicable), and "Cowl panel trim remove + reinstall" (6644 19XX). Diagnostic time (GFF) and road test times are not subject to additional allowance. All warranty claims must adhere to the Audi Warranty Policies and Procedures Manual, and claims are subject to audit by Audi Warranty.

Important Warnings

Owners should be aware that "If the vehicle is outside any warranty, this Technical Service Bulletin is informational only." This means that if your Audi is no longer under its standard or CPO warranty, you may be responsible for the cost of diagnosis and repair for the hard brake pedal starting issue.

Bulletin History

This Technical Service Bulletin, 47 22 16 2055646/4, was issued on August 11, 2022. It supersedes a previous bulletin, Group 47 number 22-12, dated June 9, 2022, with updates including added model years and revised service procedures.

NHTSA ID: 10217691