Functional Overview:

The DM-TL is located in the drivers side rear wheel well in the M5.

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 restricted 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 restricted.
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 Functional Overview

Courtesy of BMW OF NORTH AMERICA, INC.