Introduction to On Board Diagnostics (II)

OBD II monitors more components and systemsthan OBD-I, including:• Catalytic converters• Evaporative control System• Emissions control system• Emissions related powertrain performance - Oxygen sensor• Emissions related sensors and actuators- EGR monitoring• Detection of engine misfire• PCV (Positive Crankcase Ventilation) (implementation: 2002 - 2004)• Fuel system - closed loop fueling performance• Thermostats (implementation: 2000 - 2002)Components are monitored for :uCircuit continuity and out of range values of sensors, actuators, , switches, and wiresuFunctional checks for output components listed aboveuReasonable value checks during vehicle operation such as rationality, sanity, or logic checks forinput components, and output components where applicable.Thermostat monitoring is the new addition to the existing OBD II requirements. This isrequired due to:uThermostat degradation can extend the time of open-loop operation at start-upuProlonged open-loop operation will increase emissionsu“warmed-up” coolant temperature is a must for all OBD II monitoring operations.New requirements for thermostats for 2000-2002 2002 implementation include the following:uDetection of malfunctions that will affect the coolant temperature re and disable OBD II monitoring functions due to lower thannormal temperature operation of the vehicleuDetection of malfunctions that will prevent vehicle from reaching g normal operating temperature.PCV (Positive Crankcase Ventilation) failure will increase the emissions eby 1.2 g/mi for Hydro Carbons per vehiclePCV must be monitored for this reason and its requirements are:Detect PCV hose disconnections that can cause increased emissionsMeet all design guidelines concerning hoses and valve connections s and materials to ensurepositive crankcase ventilation.