Monitored Emission Control Systems

The OBD II system monitors all emission control systems that are on-board, but not all vehicles need every possible emission control system. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following; if equipped:

• The air conditioning system
• The catalytic converter efficiency
• Comprehensive component monitoring - Emission related inputs and outputs
• The evaporative emission (EVAP) system
• The fuel delivery system
• Heated catalyst monitoring
• Misfire monitoring
• The oxygen sensor system (O2S or HO2S)
• The oxygen sensor heater system (HO2S heater)

For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table . Systems such as misfire and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.