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    Re: BMW X5 3.0 TD - Excess smoke, code 0501 EGR negative control deviation # Archived Message

    Posted by Dave Harney on September 30, 2009, 2:34 pm, in reply to "BMW X5 3.0 TD - Excess smoke, code 0501 EGR negative control deviation #"

    Air mass system test diesel 4-cylinder and 6-cylinder
    Air mass system
    The air mass system consists of several component groups that ensure the optimum fresh air supply to the engine at every operating point. Malfunctions in these component groups cause a variety of disturbances in driving operation, for example lack of power, black smoke, etc.

    The air mass system test runs an overall check of the air mass system and thus allows clear pinpointing of the cause of the fault to the defective component group(s).

    Component groups of the air mass system
    The air mass system consists of:

    •Turbo pressure sensor

    •Intake-air temperature sensor

    •Charge-air temperature sensor

    •Mass air flow sensor

    •The exhaust-gas recirculation controller comprises the EGR valve, pressure transducer, pneumatic and electrical activation of the pressure transducer

    •Turbocharger pressure adjuster, comprises turbocharger with adjustment, electrical activation of the turbocharger pressure adjuster

    •Swirl flaps

    •Air filter, air hoses, pipes, charge air cooler, exhaust system, etc.

    Test procedure
    1.The charge-air pressure sensor is checked for indication of plausible values.

    2.The intake-air temperature sensor and charge-air temperature sensor are checked for signal plausibility.

    3.The mass air flow sensor is checked at output speed and idling by a comparison between measured and theoretically calculated air mass (exact description, see test module and function test instructions ”Mass air flow sensor”).
    At the same time, there is a check as to whether the system builds up the charge-air pressure quickly enough and to a high enough level.

    4.Function check of the exhaust recirculation control valve and the charge-air pressure actuator/turbocharger by means of the following automatic test procedure:

    ◦Activation of the turbocharger pressure adjuster at minimum pulse duty factor

    ◦Gradual opening of the exhaust-gas recirculation controller, measurement of the air-mass change

    ◦Closure of the exhaust-gas recirculation controller

    ◦Activation of the charge-air pressure actuator at maximum pulse duty factor

    ◦Gradual opening of the exhaust-gas recirculation controller, measurement of the air-mass change

    The idling speed is automatically increased for this test.

    5.The measured changes in air mass flow are automatically analysed. They are compared with one another in such a way that conclusions can be drawn as to the function of the exhaust-gas recirculation controller, the exhaust gas recirculation actuator and the turbocharger.

    Evaluation of the test
    The program automatically evaluates the test and specifies the procedure for any further troubleshooting.

    Caution: If incorrect measured values are specified for the mass air flow sensor and at the same time for another component group, the fault on the mass air flow sensor is likely to be a secondary fault. For this reason, fault elimination must be started at the other component group. The air mass system test must then be repeated in order to check the mass air flow sensor once again.

    The measured data on which the automatic analysis is based is also displayed after the test. It is printed out on the diagnosis report and can be used for the assessment of problem cases.

    Evaluated and displayed measured values
    Displayed value
    Definition

    Calculated air mass
    Calculated air mass from operating data at output speed and idling

    Measured air mass
    Measured air mass from mass air flow sensor at output speed and idling

    Reduction TV60 - TV70
    Reduction of air mass flow with incremental EGR activation of between 60 % and 70 %

    Increase TV60-65
    Increase in the reduction of EGR activation 60 % to EGR activation 65 %

    Increase TV65-70
    Increase in the reduction of EGR activation 65 % to EGR activation 70 %

    Difference TV60,
    Difference TV65
    Difference in the reduction at 60 % and 65 % EGR activation in each case between minimum and maximum activation of the charge-air pressure actuator


    The measured charge-air values are also displayed.

    Influence of the swirl flaps
    A malfunction on the part of the swirl flaps has only a slight effect on the air mass flow system test.

    When driving, a malfunction of the swirl flaps has the following effects:

    •Swirl flaps stick in closed position: lack of power at high engine speeds

    •Swirl flaps stick in closed position: deterioration of exhaust emissions

    Air mass system test diesel 4-cylinder and 6-cylinder
    Instructions for function test
    To ensure that the air mass system test provides a meaningful result, the test prerequisites listed below must be met without fail.

    Preconditions for the test:
    •The engine must be at operating temperature.

    •All auxiliary loads such as rear window heating or air conditioning system, must be switched off.

    •No electrical faults in the following systems may be stored in the DDE fault memory:

    ◦Charge-air-pressure control

    ◦Exhaust-gas recirculation

    ◦Air-mass flow sensor

    ◦Turbo pressure sensor

    ◦Intake-air temperature sensor

    ◦Charge-air temperature sensor

    ◦Atmospheric pressure sensor

    •Intake-air duct and exhaust system must be OK.

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