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 | ||
| EGR | P0401, P0404, P0405, P1404 | ||
| EVAP | P0440, P0442, P0446, P1441 | ||
| Oxygen Sensor | P0133, P0140, P0153, P1133, P1134, P1153, 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.