Introduction to On Board Diagnostics (II)

________________________________________________________________________________Oxygen sensor Illuminate MIL when the switchingMonitor response time of two lambdamonitoring frequency of the control-loop loop exceeds sensors in front and rear of thepredefined limit. Check input t circuit catalytic converter. Lambda sensorvoltage for detecting short circuit reacts slower on variations of the A/For open circuit. Bias is 0.450 0 volts. mixture, thus increasing the period ofthe lambda sensor regulation whichis the inverse of the closed-looploopfrequency.____________________________________________________________________________________EGR monitoring Illuminate MIL when EGR operation Monitor manifold temperature change,fails to indicate increasemanifold pressure change, on EGR flow w andin Manifold pressure orengine RPM change as well. Use sensorsfails to indicate increase in to detect these changes.manifold intake temperature or .decrease of about 50 engine RPM.EGR can be intrusively induced d duringnormal operation, or interruptedtedwhen EGR operation is occurring andmonitor these changes.___________________________________________________________________________Secondary Air Illuminate MIL when lambda sensorMonitor lambda sensor reading whensystem monitoring deviation does not correlate withsecondary air is introduced into thesecondary air flow changes. . exhaust manifold or catalyticIn open-loop operation, the air flow converter’s second chamber.should be into exhaust manifoldprovided manifold temperature is_______________________________________________________________________________below threshold and engine load isbelow threshold. In closed-looploopoperation the air flow should beinto catalytic converter’s s secondchamber in three-way catalytic converter.