Functional description
The diagnosis module for tank leakage is located on the activated carbon filter.
The leak test of the tank-ventilation system takes place after the drive cycle after stopping the engine. Various processes run in the after-run time of the engine management system:
| Index | Explanation |
|---|---|
| 1 | Fuel tank leakage diagnosis module |
| 2 | 4-pin plug-in connection |
| 3 | Connection for tank vent line |
| 4 | Dust filter |
| 5 | Activated carbon filter |
| 6 | Connection for scavenging air line |
The tank-leak diagnosis carried out within the framework of OBD 2 is based on the overpressure method. The tank-leakage diagnosis indicates a leakage where the diameter is greater than 0.5 mm and 1 mm. During the course of diagnosis, the tank-ventilation valve closes the connection to the intake pipe. At the start of the diagnosis, the leakage diagnosis pump pumps via a defined leakage of 0.5 mm diameter. The necessary current consumption is stored as an internal reference value. This is followed by the actual tank-leak diagnosis. The leak diagnosis pump pumps air into the tank-ventilation system. The current used is continuously measured. The comparison between the currently used current and the stored reference current indicates the type of leak (minor leak, superfine leak).