Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.