Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Monitored Emission Control Systems
OBD-II system monitors all emission control systems. OBD-II regulations require monitoring of the following:
- Air conditioning system.
- Catalytic converter efficiency.
- Evaporative Emissions (EVAP) system.
- Exhaust Gas Recirculation (EGR) system.
- Fuel delivery system.
- Heated catalyst monitoring.
- Misfire monitoring.
- Oxygen sensor system (O2S or HO2S).
- Oxygen sensor heater system (HO2S heater).
- Secondary Air Injection (AIR) system.
For specific DTCs required for each system, see INSPECTION/MAINTENANCE SYSTEM DIAGNOSTIC TROUBLE CODES table. Systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously on some vehicles, and may not require an indicator.
| I/M System | (1) DTC | ||
|---|---|---|---|
| AIR | P0410, P1415 & P1416 | ||
| Catalyst | P0420 & P0430 | ||
| EVAP | P0440, P0442, P0446 & P1441 | ||
| Oxygen Sensor | P0133, P0153, P1133, P1153, P1134 & P1154 | ||
| Oxygen Sensor Heater | P0135, P0141, P0155 & P0161 | ||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.