Introduction to On Board Diagnostics (II)

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Functionality of PowertrainControl Module (PCM) inOBD IIPerform powertrain control functions to reduce emissionsand meet OBD II regulations in closed-loop loop controlduring normal operation.Closed-loop mode of control is selected by PCM when the lambda sensor hasattained a temperature more than 300 0 C. The intake Air/Fuel ratio iscontrolled in a closed loop by measuring the EGO at the exhaust manifoldand altering the input fuel flow rate with fuel injector to correct for a rich orlean mixture indication. The PCM continuously adjusts the output signal tothe fuel injector to maintain stoichiometry by varying the duty cycle. Variationsin engine transport delay with RPM are corrected by reducing the cyclefrequency and duty cycle ramp rate with decreasing RPM. The fuel flow iscorrected by using fuel trim correction using short term update and longterm update scheme, to compensate for the engine performance over time.
Functionality of PowertrainControl Module (PCM) inOBD IIPerform powertrain control functions to reduce emissionsand meet OBD II regulations in closed-loop loop control.Acceleration Enrichment: When heavy load is demanded by the driver, thePCM adjusts the fuel control to provide enriched air/fuel mixture to maximizeengine torque and neglect emission control. This is for short time and isapproved by EPA. The PCM performs this by detecting high throttling anglesensor voltage or high MAP sensor value. In case WOT, the PCM increases theduty cycle of the fuel injector to the maximum allowed value, which may resultin A/F ratio of as low as 12:1.
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Introduction to On BoardDiagnostics
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OBD II monitors more components and
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Powertrain and EmissionControls in
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Powertrain and EmissionControl in P
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OBD II for L & MD VehiclesSTD Manua
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OBD II for L & MD VehiclesDiagnosti
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Fundamentals of PowertrainControl s
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The Freeze Frame can also be used f
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Evaporative System Monitoring: Hydr
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OBD(II)In addition the electrical c
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Introduction to On Board Diagnostics (II)

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