Air mass system test M57
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.
Component groups of the air mass system
The air mass system consists of:
- Charge-air-pressure sensor
- Intake Air Temperature Sensor
- Air-mass flow sensor
- The exhaust-gas recirculation controller comprises the EGR valve, pressure transducer, pneumatic and electrical activation of the pressure transducer
- The charge-air pressure actuator comprises the turbocharger with adjustment, pressure transducer, pneumatic and electrical activation of the pressure transducer
- Swirl flaps (in all series except for X5), in cars as of 03/2000 with automatic gearbox
- Air filter, air hoses, pipes, charge air cooler, exhaust system, etc.
Test procedure
- The charge-air-pressure sensor is checked for indication of plausible values.
- Intake-air temperature sensor is checked for indication of plausible values
- The air-mass sensor is checked during idling and at 3500 rpm by a comparison of measured and theoretically calculated air mass (for a detailed description, refer to the test module ”Air-mass sensor”).
- Proceed as follows for perform an operational test of the exhaust-gas recirculation controller and the charge-air pressure actuator:
- Activation of the charge-air pressure actuator 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
For this test, the idling speed is increased automatically; the test is also automatic.
- The measured air-mass changes are automatically evaluated and related to one another in such a way that conclusions can be drawn with regard to the function of the exhaust-gas recirculation controller and the charge-air pressure actuator.
Evaluation of the test
The program automatically evaluates the test and specifies the procedure for any further troubleshooting.
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 usesd for the assessment of problem cases.
Evaluated and displayed measured values
Displayed value
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Definition
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Calculated air mass
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Calculated air mass from air-mass sensor in idling and at 3500 rpm
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Measured air mass
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Measured air mass from air-mass sensor in idling and at 3500 rpm
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Reduction TV60 - TV75
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Reduction of air mass with EGR activation of 60% to 75%
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Increase TV60-65
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Increase in the reduction of EGR activation 60% to EGR activation 65%
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Increase TV65-70
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Increase in the reduction of EGR activation 65% to EGR activation 70%
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Difference TV60 - TV75
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Difference in the reduction at 60% to 75% EGR activation in each case between minimum and maximum activation of the charge-air pressure actuator
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Influence of the swirl flaps
The program opens the swirl flaps at the start of the test of the exhaust gas recirculation and charge-air-pressure control. A malfunction on the part of the swirl flaps has only a slight influence on the air mass 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 emissions