| Diagnostic Trouble Codes | Scan for stored, pending, and permanent emissions-related codes. | No active emissions fault codes; do not erase codes immediately before inspection. | A fault code can turn on the malfunction indicator lamp and may cause an automatic inspection failure under local rules. | Clear / Verified |
| Malfunction Indicator Lamp | Turn the ignition on without starting the engine, then start the vehicle. | The warning lamp illuminates briefly during the bulb check and goes out after the engine starts. | A lamp that remains on indicates a detected emissions or engine-management fault. | Lamp Off |
| Continuous Monitors | Check misfire, fuel-system, and comprehensive-component monitors. | These monitors normally run continuously while the vehicle is operating and should report complete when no fault prevents testing. | They evaluate core engine-control functions that can directly affect emissions. | Ready |
| Catalyst Monitor | Confirm that the catalytic-converter efficiency monitor has completed. | Monitor shows Ready after the vehicle has experienced suitable operating conditions. | The monitor compares oxygen-sensor behavior to assess catalyst performance. | Ready |
| Oxygen Sensor Monitor | Check the oxygen-sensor response and activity monitor. | Monitor shows Ready with no related sensor fault code. | Oxygen sensors help control the air-fuel mixture and support emissions testing. | Ready |
| Oxygen Sensor Heater Monitor | Verify that the oxygen-sensor heater monitor has completed. | Monitor shows Ready and no heater-circuit fault is stored. | The heater allows the sensor to reach operating temperature quickly, especially after a cold start. | Ready |
| Evaporative System Monitor | Check the fuel-vapor leak and purge-system monitor. | Monitor shows Ready; fuel cap is properly installed and the fuel level is within the vehicle’s required test range. | It detects fuel-vapor leaks that can increase hydrocarbon emissions. | Ready |
| Exhaust Gas Recirculation / Variable Valve Timing | Check whether the vehicle is equipped with an EGR or valve-timing monitor and verify its status. | If supported, the monitor shows Ready with no related fault code. Some vehicles do not use this monitor. | These systems can reduce combustion temperatures or optimize engine operation to control emissions. | Ready if Equipped |
| Secondary Air Injection | Check the secondary-air monitor when the vehicle is equipped with this system. | If supported, the monitor shows Ready and the related pump, valve, and sensor circuits pass their checks. | Additional air may be introduced during cold operation to help reduce emissions and warm the catalyst. | Ready if Equipped |
| Heated Catalyst | Check the heated-catalyst monitor if the vehicle supports it. | If supported, the monitor shows Ready with no related fault code. | The system is designed to bring the catalyst to effective operating temperature more quickly. | Ready if Equipped |
| Readiness After Battery Disconnection | Check whether the battery was disconnected, replaced, or allowed to go completely flat. | All required monitors have completed again before inspection. | Loss of power commonly resets readiness monitors to Not Ready and may also erase stored diagnostic information. | Recheck Required |
| Drive-Cycle Completion | Follow the vehicle manufacturer’s drive-cycle conditions, including cold starts, steady-speed driving, deceleration, and varied engine loads. | Drive until every monitor required by the vehicle and local inspection program reports Ready. | Different monitors require different temperatures, speeds, fuel levels, and operating conditions; one short trip may not complete them all. | Confirm with Scanner |
| Warm-Up and Fuel Level | Allow the engine to reach normal operating temperature and keep the fuel level within the vehicle’s specified range. | Engine temperature is normal; fuel level is neither nearly empty nor overfilled. | Temperature and fuel-level conditions can prevent catalyst or evaporative-system tests from running. | Condition Met |
| Recent Repairs | After repairs, scan again and confirm that no new codes or pending codes have appeared. | Repair is verified, warning lamp remains off, and required monitors are Ready. | A repaired vehicle can still fail if a monitor has not completed or if a fault is pending. | Verify Before Test |
| Inspection-Day Preparation | Bring required documents, arrive with the engine warmed up, and avoid clearing codes before the test. | Vehicle identification and registration documents meet local requirements; scan data is unchanged and complete. | Inspection procedures and the number of permitted Not Ready monitors vary by jurisdiction, vehicle age, and vehicle type. | Ready to Inspect |