2002 2BMXV04.4LEV, 2BMXT04.4E53 & 2BMXT04.6XHP

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Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of .019" (.5 mm) and greater. Using a Diagnostic Module-Tank Leakage (DM-TL) connected to an electrical actuated pump located at atmospheric connection of evaporative canister, a pressure test of evaporative system is performed in following order:
- During reference leak measurement, electrical actuated pump delivers through the reference restriction. See Fig 1. Engine management system measures pump electrical current consumption.
- During leak measurement, electrical actuated pump delivers through charcoal canister into fuel tank system. Pressure in evaporative system may be up to 25 kPa depending on fuel level in tank. Engine management system measures pump electrical current consumption. A comparison of currents of reference leak measurement and leak measurement is a measure for leakage in tank. See Fig 2.
- After 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
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Fig 2: Leak Measurement
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Fig 3: Bleeding Off Remaining Pressure
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Monitoring Structure Of Leak Measurement - See Fig 4-Fig 6 .

Fig 4: Monitoring Structure Of Leak Measurement (1 Of 3)
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Fig 5: Monitoring Structure Of Leak Measurement (2 Of 3)
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Fig 6: Monitoring Structure Of Leak Measurement (3 Of 3)
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Diagnosis Frequency & MIL Illumination - See Fig 7-Fig 8 .

Fig 7: No Refueling Detected; Leak Greater Than .039" (1.0 mm)
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Fig 8: Refueling Detected; Leak Greater Than .019" (.5 mm)
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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.
Monitoring Structure Of Evaporative Purge System Flow Check (Test Groups 2BMXV04.4LEV, 540i; 2BMXT04.4E53, X5 4.4L; and 2BMXT04.6XHP, X5 4.6L)
- 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. See Fig 9.
- Step 2 - For A Stoichiometric Mixture - 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. Effect of additional cylinder charge triggers a variation of engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed. To start diagnosis function (step 2) several conditions have to be satisfied:
  1. Vehicle speed = 0.
  2. Engine at idle speed.
  3. Closed loop of lambda controller.
  4. Coolant temperature greater than fixed limit.
In addition, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later.

Fig 9: Evaporative Purge System Flow Check (Test Groups 2BMXV04.4LEV, 2BMXT04.4E53 & 2BMXT04.6XHP)
Courtesy of BMW OF NORTH AMERICA, INC.
Monitoring Structure Of Evaporative Purge System Flow Check (Test Group 2BMXV04.4LEV Models 745i & 745Li)
- 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. See Fig 10.
- Step 2 - For A Stoichiometric Mixture - 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. Effect of additional cylinder charge triggers a variation of engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed. To start diagnosis function (step 2) several conditions have to be satisfied:
  1. Vehicle speed = 0.
  2. Engine at idle speed.
  3. Closed loop of lambda controller.
  4. Coolant temperature greater than fixed limit.
  In addition, diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later.
  
  Fig 10: Evaporative Purge System Monitoring Structure (Test Group 2BMXV04.4LEV)
  Courtesy of BMW OF NORTH AMERICA, INC.
- Step 3 - In case of a high load in idle, a variation of engine idle speed cannot be measured correctly in Step 2. Therefore, purge valve will be opened after EVAP leak detection has finished. When valve opens, pressure and also pump current will drop. If pump current is greater than threshold, purge valve is operational.