2002 2BMXV03.2S54 & 2BMXV04.9S62

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Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of .039" (1.0 mm) and up. By means of a Diagnostic Module-Tank Leakage (DM-TL), a electrical actuated pump located at atmospheric connection of evaporative canister, a pressure test of evaporative system is performed in the following order:
- During reference leak measurement, electrical actuated pump delivers through reference restriction. Engine management system measures pump electrical current consumption in this section. See Figure.
- 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 Figure.
- During pressure test, purge valve needs to be shut. After test, canister purge is resumed, remaining pressure in the evaporative system is bled off. See Figure.
Evaporative System Monitoring Structure - See Fig 1-Fig 2 .

Fig 1: Evaporative System Monitoring Structure (1 Of 2)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Evaporative System Monitoring Structure (2 Of 2)
Courtesy of BMW OF NORTH AMERICA, INC.
Diagnosis Frequency & MIL Illumination - See Figure and Fig 3-Fig 7 .

Fig 3: Diagnostic Frequency & MIL Illumination (After Refueling Detected & No Leak)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 4: Diagnostic Frequency & MIL Illumination (After Refueling Detected & Filler Cap Left Open; 2BMXV04.9S62)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 5: Diagnostic Frequency & MIL Illumination (After Refueling Detected & Filler Cap Left Open; 2BMXV03.2S54)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 6: Diagnostic Frequency & MIL Illumination (After Refueling Detected & CHECK FILLER CAP Message Ignored; 2BMXV04.9S62)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 7: Diagnostic Frequency & MIL Illuminated (After Refueling Detected & CHECK FILLER CAP Message Ignored; 2BMXV03.2S54)
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 8.

Fig 8: Monitoring Structure Of Evaporative Purge System Flow Check
Courtesy of BMW OF NORTH AMERICA, INC.
Monitoring Cycle 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 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 a fixed limit.
  Furthermore, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later.
- Engine idle speed variation less than a fixed limit.