Test Group 1BMXV04.4LEV& 1BMXT04.4E53

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2001 BMW Z8, 2001 BMW X5, 2001 BMW M5, 2001 BMW 750iL, and 2001 BMW 740iL. However, it is still accessible from the selected car via links, so may be relevant.

Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of .019" (0.5 mm) and greater. Using a Diagnostic Module Tank Leakage (DM TL), an electrically 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, electrically actuated pump delivers through reference restriction. Engine management system measures pump electrical current consumption in this section. SeeFig 1.
- 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.
- During PRESSURE TEST, purge valve needs to be shut. After test, canister purge is resumed and consequently remaining pressure in evaporative system is bled off. 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: Pressure Test
  Courtesy of BMW OF NORTH AMERICA, INC.
Monitoring Structure Of Leak Measurement - See Fig 4-Fig 5 .

Fig 4: Monitoring Structure Of Leak Measurement (1 Of 2)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 5: Monitoring Structure Of Leak Measurement (2 Of 2)
Courtesy of BMW OF NORTH AMERICA, INC.
Diagnosis Frequency & MIL Illumination - See Fig 6-Fig 7 .

Fig 6: Diagnosis Frequency & MIL Illumination For Leak Greater Than .039" (1 mm)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 7: Diagnosis Frequency & MIL Illumination For 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.
Monitoring Cycle Of Evaporative Purge System Flow Check - See Fig 8.
- 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, several conditions have to be satisfied:
  
  Fig 8: Evaporative Purge System Flow Check
  Courtesy of BMW OF NORTH AMERICA, INC.
  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.
    - Engine idle speed variation is less than a fixed limit.
Evaporative System Leak Measurement With LDP (740i & 740iL) - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of 1.0 mm and larger. By means of a Leak Detection Pump (LDP), a vacuum actuated pump located at the atmospheric connection of the evaporative cane test of the evaporative system is performed in the following order:
- During FAST PULSE PHASE evaporative system is set under a defined pressure. Pressure in evaporative system after FAST PULSE PHASE may be higher or lower than defined pressure depending on fuel level in tank.
- NATURAL FREQUENCY PHASE that follows PAST PULSE PHASE is therefore needed to adjust pressure to its correct value.
- During final measurement, phase of time between pump strokes of LDP is evaluated. In case of a time between pump strokes below a preset threshold, a leak is assumed to be present.
During pressure test, purge valve needs to be shut. After test canister purge is resumed and consequently the remaining pressure in evaporative system is bled off. To have maximum capacity (or minimal loss of purge air due to leak detection) test normally runs after engine cold start. However, under certain circumstances test may be preliminary aborted and started again later during engine run if all conditions for restart of test are met.
Monitoring Structures Of Leak Measurement (LDP) - Cold start conditions/monitoring structure. See Figure.
Cold Start Condition: Use Of Ambient Temperature Signal Provided By Vehicle Can Bus (740i & 740iL) - The Leak Detection Pump (LDP) component is specified for defined temperature range. To prevent the component from being operated under unspecified conditions, ambient temperature is used as a condition for starting monitoring sequence after cold start. Ambient temperature signal is checked for circuit continuity later in driving cycle by means of intake air temperature monitor (TAL REF monitor):
- At the time of engine start the value of TAL REF is initialized to the maximum possible value.
- If a specified load and a specified vehicle speed is exceeded over a specific time the value of TAL REF is updated with the value provided by the intake air temperature sensor. This however is only done if the intake air temperature value is lower than the value that is already represented by TAL REF, Thus TAL REF always represents the minimum value of the intake air temperature sensor found during the conditions mentioned above.
  Using this technique the following sequences are possible:
  - Ambient temperature is within specified range and no leak is detected during the monitor sequence. In this case, system is considered to be without a leak and no fault code is stored.
  - Ambient temperature is within specified range and a leak is detected during monitoring sequence. After conditions for updating TAL REF are met and TAL REF is within specified range, a fault code is stored. In case TAL REF is out of specified range, no fault code is stored.
  - Ambient temperature is out of specified range at time of engine start: This leads to a preliminary cancellation of the monitoring sequence, the monitoring sequence is carried out as soon as all conditions for repetition after a preliminary abort.
Condition For Preliminary Abort (740i & 740iL) - See Figure.
Condition For Preliminary Abort, Downhill Run Detection (740i & 740iL) - The LDP measures the difference between the internal tank pressure and the ambient pressure. In case of a vehicle moving downhill the internal tank pressure remains constant whereas ambient pressure increases. Consequently, pressure difference measured by the LDP decreases which may cause the detection of a leak that is not present (i. e. false alarm). To prevent this, a downhill run detection that compares engine torque with a torque that is needed for driving the car on level terrain at a given speed, is implemented. Once a downhill run is detected, monitoring sequence is preliminary aborted. See .Figure, Figure, Figure and Fig 9 .

Fig 9: Identifying Evaporative System (740i & 740iL)
Courtesy of BMW OF NORTH AMERICA, INC.
Evaporative Purge System Flow Check (740i & 740iL) - The 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 Figure.