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
The OBD II System monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with Exhaust Gas Recirculation (EGR). The OBD II regulations require monitoring of the following::
- Comprehensive component monitoring -- Emission related inputs and outputs.
- Exhaust gas recirculation (EGR) system.
- Misfire monitoring.
| System | DTCs Required To Set System Status To YES | |
|---|---|---|
| Component Monitoring | P0236, P0741, P0742 | |
| Exhaust Gas Recirculation (EGR) | P0101, P0401, P0404, P2279 | |
| Misfire Monitoring | P0300, P0301-P0308 | |
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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.