2003 BMXV03.0LER, 3BMXV03.0M5R, 3BMXT03.0E5R & 3BMXV02.5M56

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Leak Measurement Description - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of .019" (.5 mm) and up. By means of a Diagnostic Module-Tank Leakage (DM- TL), an electrical actuated pump located at the atmospheric connection of the evaporative canister, a pressure test of the evaporative system is performed in the following order:
- During the Reference Leak Measurement, the electrical actuated pump delivers through the reference restriction. The engine-management system measures the pump's electrical current consumption in this section. See Fig 1.
- During leak measurement, electrical actuated pump delivers through charcoal canister into fuel-tank system. The pressure in the evaporative system may be up to 25 hPa depending on fuel level in tank. Engine-management system measures pumps electrical current consumption. A comparison of the currents of the reference leak measurement and the leak measurement is a measure for the leakage in the tank. See Fig 2.
- After the test, remaining pressure in evaporative system is bled off through charcoal canister by switching off pump and solenoid. See Fig 3.
  
  Fig 1: Reference Leak Measurement
  Courtesy of BMW OF NORTH AMERICA, INC.
  
  Fig 2: Leak Measurement
  Courtesy of BMW OF NORTH AMERICA, INC.
  
  Fig 3: Bleeding Off Remaining Pressure
  Courtesy of BMW OF NORTH AMERICA, INC.
Monitoring Structure Of Leak Measurement - See Fig 4-Fig 6

Fig 4: Monitoring Structure Of Leak Measurement (1 Of 3)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 5: Monitoring Structure Of Leak Measurement (2 Of 3)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 6: Monitoring Structure Of Leak Measurement (3 Of 3)
Courtesy of BMW OF NORTH AMERICA, INC.
Diagnosis Frequency & MIL Illumination - Fig 7-Fig 8 .

Fig 7: No Refueling Detected; Leak Greater Than .039" (1.0 mm)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 8: Refueling Detected; Leak Greater Than .019" (.5 mm)
Courtesy of BMW OF NORTH AMERICA, INC.
Evaporative Purge System Flow Check - Purge flow from charcoal canister through purge valve is monitored after fuel system adaptation is completed and lambda controller is at closed loop condition. Diagnosis is started during regular purging. See Fig 9.

Fig 9: Monitoring Structure Of Evaporative Purge System Flow Check
Courtesy of BMW OF NORTH AMERICA, INC.
Monitoring Process Of Evaporative Purge System Flow Check
- Step 1 - For Rich Or Lean Mixture - Flow through purge valve is assumed as soon as lambda controller is compensating for a rich or a lean shift. After this procedure, diagnosis is completed and evaporative purge system resumes working normally.
- Step 2 - For Stoichiometric Mixture Or If First Step Fails - In this case lambda controller does not need to compensate for a deviation. Therefore, after finishing regular purging, purge valve is opened and closed abruptly several times. The effect of additional cylinder charge triggers a variation of engine idle speed. If a predetermined value is reached, diagnosis procedure is completed.
- Step 3 - For Stoichiometric Mixture Or If Second Step Fails - If threshold at 2nd step is not reached, an additional procedure is performed. Purge valve is opened and the idle air control valve simultaneously is closed to compensate idle speed increase. The effect is a decrease of measured idle air mass by mass airflow sensor. If a predetermined value is reached, diagnosis procedure is completed. See Fig 10.
  
  Fig 10: Monitoring Structure Of Evaporative Purge System Flow Check
  Courtesy of BMW OF NORTH AMERICA, INC.