Functional Overview:

The DM-TL is located next to the charcoal canister on the E46.

1. In it's inactive state, filtered fresh air enters the evaporative system through the sprung open valve of the DM-TL.
2. When the DME activates the DM-TL for leak testing, it first activates only the pump motor. This pumps air through a restrictor orifice (1.0 or 0.5 mm) which causes the electric motor to draw a specific amperage value. This value is equivalent to the size of the restrictor.
3. The solenoid valve is then energized which seals the EVAP system and directs the pump output to pressurize the EVAP system.

   The EVAP system is detected as having a large leak if the amperage value is not realized, a small leak if the same reference amperage is realized or no leak if the amperage value is higher than the reference amperage.

   Fig 1: DM-TL Operational Modes

   Courtesy of BMW OF NORTH AMERICA, INC.