2021-2023 Audi MIL On P045600 Small Leak Detected TSB

Symptoms

Owners of affected 2021-2023 Audi A4, A5, S4, S5, and RS 5 models may notice the "exhaust emissions warning lamp (MIL) is on" in their instrument cluster. This indicates a potential issue with the vehicle's emissions system.

Fault Codes / DTCs

When diagnosing this issue, technicians may find the following Diagnostic Trouble Code (DTC) stored in the vehicle's event memory:

• DTC P045600 (P0456) – "Very Small Leak Detected"

This specific code points to a very small leak within the evaporative emissions system.

Technical Background

Audi has identified that even the smallest contamination can lead to an internal leak in the fuel tank pressure sender G400, also known as the Natural Vacuum Leak Detection (NVLD) unit. This internal leak is the root cause for the "Audi P045600 Very Small Leak" error and the illumination of the MIL.

Important Warnings for Repair

During the repair process involving the NVLD, it is crucial to follow specific instructions to prevent damage:

• Do NOT close or expose to compressed air the opening marked with a red circle on the NVLD component. Doing so can cause irreparable damage to the NVLD. This specific opening is designed to help blow out contamination.
• When using compressed air to blow through the NVLD, do NOT clamp or secure the component in a vice. Always hold the component in your hand to avoid the risk of damage.

Repair Procedure Summary

If your Audi is experiencing the "Audi P045600 Very Small Leak" issue, the service procedure involves a multi-step approach:

1. Initial Inspection: The technician will first ensure there are no external leaks in the fuel system by performing checks according to the Guided Fault Finding (GFF) system or the Workshop Manual.
2. Sender Removal (if necessary): If the GFF system indicates, the fuel tank pressure sender G400 (NVLD) will be removed as specified in the Workshop Manual.
3. Cleaning Procedure: Using a compressed air gun, the technician will blow through the NVLD (item 12 in the illustration provided in TSB 2071199/1) with several brief pressure applications of approximately 5 bar. This is done through the opening on the NVLD marked by a green arrow in the illustration.
4. Reinstallation and Recheck: After the cleaning, the fuel tank pressure sender G400 (NVLD) is reinstalled, and the system is rechecked for any leaks.

This procedure aims to clear any contamination causing the internal leak and resolve the "Very Small Leak Detected" fault.

Warranty Information

This repair, identified by TSB 2071199/1, may be covered under warranty for eligible vehicles. For new vehicles, coverage typically extends up to 48 months or 50,000 miles. For Certified Pre-Owned (CPO) vehicles, coverage is designated by claim type G10, requiring verification of owner eligibility. If the vehicle is outside of any applicable warranty, this Technical Service Bulletin serves as informational guidance for diagnosis and repair.

Owner Action

If your 2021-2023 Audi A4, A4 allroad, A5, S4, S5, or RS 5 has the "exhaust emissions warning lamp (MIL) is on" or you suspect an "Audi P045600 Very Small Leak", it is recommended to schedule an appointment with an authorized Audi service center. Provide them with the symptom description and mention Technical Service Bulletin 2071199/1 for efficient diagnosis and repair.

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Source: NHTSA ID: 10241211