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.Deceleration Enleanment and Idle Speed Control: When the driverdecelerates the vehicle very hard, the PCM reduces the engine torque bycutting off fuel , with decel fuel cut off mode in which the fuel injector isturned off or the duty cycle is drastically reduced. A typical algorithm forfuel injection duration for the desired Air/Fuel ratio of stoichiometry is given by:T = base pulse width from lookup table for mass air flow + closed loopcorrection factor closed loop correction factor is the fuel trim block learn valuealluded earlier.For open-loop control , closed-loop correction factor is zero.For closed-loop operation, correction factor, C, is given by:C = I*A + B*F, where A and B are constants, and I is the integral part, and F isthe fractional part of the correction factor..
Functionality of PowertrainControl Module (PCM) inOBD IIPerform powertrain control functions to reduce emissionsand meet OBD II regulations.I and F are determined from the fuel trim, and EGO sensor. When EGO indicatesrich mixture , Fuel trim value I is reduced by 1, and increased by 1 for lean mixture.The base pulse width of fuel injector is proportional to mass air flow given by:T = K* R a, where factor K is determined by the PCM, depending on the Mode offuel control. For closed-loop normal operation, K corresponds to stoichiometricAir/Fuel mixture. For cold start, K corresponds to A/F = 12:1. For deceleration, K=0.The mass air flow is calculated by the PCM as described before.
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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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