2023-2026 Audi Fuel Tank Cap Leak & EVAP DTCs P045600 P044200

Audi Technical Service Bulletin (TSB) 2078916/2 addresses a common issue affecting various 2023-2026 Audi models where a twisted fuel tank cap seal can lead to the illumination of the 'MIL/exhaust emission warning light'. This condition is often accompanied by specific Diagnostic Trouble Codes (DTCs) related to the Evaporative Emission (EVAP) control system. This TSB provides a straightforward solution to resolve the Audi fuel tank cap leak P045600 and related issues.

Symptoms

Owners of affected Audi vehicles may observe the 'MIL/exhaust emission warning light is on' illuminated on their dashboard. This warning indicates a potential issue with the vehicle's emissions system, which can be triggered by a seemingly minor component like the fuel tank cap seal.

Fault Codes / DTCs

When the 'MIL/exhaust emission warning light' appears due to a fuel tank cap seal issue, the engine control module (ECM) (J623) may store one or more of the following Diagnostic Trouble Codes:

Code	Description
P045600	"EVAP Emission Control System (very small leak) leak detected"
P00EF00	(No specific description provided in TSB)
P044200	(No specific description provided in TSB)

These codes specifically point to a leak within the EVAP system, which prevents fuel vapors from escaping into the atmosphere.

Diagnosis / Trigger Conditions

Upon a customer complaint regarding the 'MIL/exhaust emission warning light', a technician will connect to the vehicle's diagnostic system. The presence of DTCs P045600, P00EF00, or P044200 in the ECM (J623) indicates that the fuel tank detection system has identified a leak. The primary diagnostic step involves inspecting the fuel tank cap seal.

Repair Procedure Summary

The repair for an Audi fuel tank cap leak P045600 is quite simple and does not typically require replacing components. The core of the procedure involves:

1. Inspection: Carefully check the fuel tank cap for a twisted or improperly seated seal. The TSB includes an image illustrating a twisted orange seal as an example.
2. Correction: If a twisted seal is identified, it should be correctly repositioned and seated. This ensures a proper seal for the fuel tank.

Important Warnings

Audi Technical Service Bulletin 2078916/2 explicitly states that "Replacing components or a smoke test is not required." This is a crucial point, as it prevents unnecessary parts replacement or diagnostic procedures that will not resolve the issue. Owners should be aware that if their vehicle is outside of its warranty period, this Technical Service Bulletin is informational only, meaning the repair may not be covered free of charge.

Owner Action

If your 2023-2026 Audi is displaying the 'MIL/exhaust emission warning light' or you suspect an Audi fuel tank cap leak P045600, it is recommended to visit an authorized Audi service center. Inform them about the symptoms and mention Audi TSB 2078916/2. The repair is typically quick, involving a simple inspection and adjustment of the fuel tank cap seal, which can prevent more extensive and costly repairs down the line.

Warranty Information

For vehicles under warranty, the labor operation for this repair is