FUEL SYSTEM, CHECKING FOR LEAKS, VEHICLES WITH Fuel Tank Pressure Sensor -G400-

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

  Courtesy of AUDI OF AMERICA, LLC

• The Fuel Tank Pressure Sensor -G400- -5- senses the vacuum in the bleeder line -6- near the EVAP canister -4-. The Fuel Tank Leak Detection Control Module -J909- -2- is attached directly to the wall of the fuel tank -1- and monitors the temperature inside the fuel tank. The system is considered to be closed if the measured vacuum is 2.5 mbar (0.036 psi). If there is no vacuum, then there is a leak in the fuel system, which will result in an entry in the engine control module DTC memory.

3 -  Signal Wire to Engine Control Module -J623-

7 -  Bleeder Line to Engine