DM-TL (Diagnosis Module - Tank Leakage): Function

The DC Motor LDP ensures accurate fuel system leak detection for leaks as small as 0.5mm (.020"). The pump contains an integral DC motor which is activated directly by the engine control module. The ECM monitors the pump motor operating current as the measurement for detecting leaks.

The pump also contains an ECM controlled change over valve that is energized closed during a Leak Diagnosis test. The change over valve is open during all other periods of operation allowing the fuel system to "breath" through the inlet filter (similar to the full down stroke of the current vacuum operated LDP).

Fig 1: Diagnosis Module - Tank Leakage Function Flow Diagram

Courtesy of BMW OF NORTH AMERICA, INC.