Tank Leak Diagnosis System (Vehicles From My 2013)

WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2016 Audi S4, 2016 Audi A4 Quattro, 2016 Audi A4, 2015 Audi S4, and 2015 Audi A4 Quattro. However, it is still accessible from the selected car via links, so may be relevant.

The function of the leak detection system is based on the premise that the fuel systems creates a natural vacuum when the fuel in the fuel tank -6- becomes colder.

Fig 1: Tank Leak Diagnosis System (From MY 2013)
Courtesy of AUDI OF AMERICA, LLC
The Fuel Tank Leak Detection Control Module -J909- -3- with integrated Fuel Tank Pressure Sensor -G400- monitors the vacuum and the temperature inside the fuel tank. The system is considered to be closed if the measured vacuum is 2.5 mbar (0.036 psi).
There is a leak in the fuel system if there is not vacuum, which will result as an entry in the control module Diagnostic Trouble Code (DTC) memory.

1 -

Breather line

2 -

EVAP canister

4 -

Bleed line to the engine

5 -

Signal wire to the Engine Control Module -J623-

7 -

Not installed