DMTL (Diagnosis Module - Evaporative Leakage Detection)

DMTL (Diagnosis Module - Evaporative Leakage Detection): This component ensures accurate fuel system leak detection for leaks as small as 0.5 mm (.02C") by slightly pressurizing the fuel tank and evaporative components. The DMTL pump contains an integral DC motor which is activated directly by the ECM. 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. The DMTL is located with the Active Carbon Canister.







1. In its inactive state, filtered fresh air enters the evaporative system through the sprung open valve of the DMTL.







2. When the ECM activates the DMTL for leak testing, it first activates only the pump motor. This pumps air through a restricted orifice (0.5 mm) which causes the electric motor to draw a specific amperage value (20-30 mA). This value is equivalent to the size of the restriction.







3. The solenoid valve is then energized which seals the evaporative system and directs the pump output to pressurize the evaporative system.
- A large leak is detected in the evaporative system if the amperage value is not achieved.
- A small leak is detected if the same reference amperage is achieved.
- The system is sealed if the amperage value is higher than the reference amperage.