Fuel Tank Leak Detection Control Module - J909-, Checking: General Description
The fuel tank has an integrated ventilation system in order to enable pressure equalization between the fuel tank and the environment when temperature variations occur or when fuel is added to or extracted from the tank. To prevent fuel evaporation to the atmosphere, a charcoal canister is installed between the fuel tank and the atmosphere. Since the charcoal canister has a limited storage capacity, it must be occasionally discharged into the intake manifold by using the evaporative emission (EVAP) canister purge valve for a short period of time. In systems without a turbocharger, an EVAP purge line from the canister purge valve to the intake manifold is sufficient. The Tank Leak Diagnostic Module (DM-TL) consists of an electrically operated air pump (DM-TL pump), an orifice with a defined diameter serving as a reference leak, and a change over valve switching the air flow between the reference leak and the tank. If neither the pump nor the change over valve is activated, the tank is ventilated through a bypass in the module. The canister purge valve can be actively checked using the DM-TL. For this purpose, the current consumption of the DM-TL pump is measured during a reference measurement and under different monitoring conditions. The pump current can be used to determine the pressure in the EVAP system and check the canister purge valve for proper operation.
The Fuel Tank Leak Detection Control Module -J909- contains the following component:
- Leak Detection Pump -V144-
The Fuel Tank Leak Detection Control Module -J909- components cannot be serviced separately, and they must be serviced as a unit.
Special tools and workshop equipment required
- Multimeter.
- Wiring Diagram.
- Scan Tool.
Test requirements
- Fuses OK.
- Battery voltage OK.
- Switch OFF all electrical and electronic accessories.
- Vehicles with automatic transmission, ensure the selector lever position is in "P".
- Vehicles with manual transmission, ensure the shifter lever position is in "N" with the parking brake applied.
- Observe all safety precautions: SAFETY PRECAUTIONS .
- View clean working conditions: CLEAN WORKING CONDITIONS .