Encountering a “Smog Obd2 Not Ready” message during a vehicle inspection can be frustrating. It means your car’s onboard diagnostic system hasn’t completed all the necessary self-tests, and therefore, it will likely fail the smog check. But what exactly does “not ready” mean, and how can you get your car ready for inspection? Let’s break it down.
Understanding OBD2 Readiness Monitors
Modern vehicles are equipped with sophisticated onboard diagnostic systems (OBD2) that continuously monitor various engine and emission control components. These monitors run self-tests to ensure everything is functioning correctly. For a smog check, most of these monitors need to be in a “ready” or “complete” state. When some monitors are “not ready,” it indicates that these self-tests haven’t been fully executed since the last time the car’s computer system was reset or interrupted.
Common monitors that might show as “not ready” include:
- Catalyst Monitor: Checks the efficiency of the catalytic converter in reducing harmful emissions.
- Evaporative System (EVAP) Monitor: Tests the evaporative emissions control system for fuel vapor leaks.
- Oxygen Sensor Monitor: Verifies the proper operation of the oxygen sensors, crucial for fuel mixture control.
- EGR System Monitor: (If applicable) Evaluates the exhaust gas recirculation system, which reduces NOx emissions.
If these, or other relevant monitors, are not in a “ready” state, your vehicle will likely fail the smog test, even if there isn’t a major underlying issue.
Why Are OBD2 Monitors “Not Ready”?
Several reasons can cause OBD2 monitors to be “not ready”:
- Recent Battery Disconnection: Disconnecting or replacing your car battery resets the OBD2 system and clears the readiness monitor status.
- ECU/PCM Reset: Any reset of the engine control unit (ECU) or powertrain control module (PCM), often done during repairs or diagnostic procedures, will also reset the monitors.
- Recent Diagnostic Trouble Code (DTC) Clearing: If you recently cleared any engine fault codes, the monitors will be reset to “not ready.”
- Interrupted Drive Cycles: The OBD2 system requires specific driving patterns, known as “drive cycles,” to run and complete all the self-tests. If these drive cycles are interrupted or not completed correctly, monitors may remain “not ready.”
- Underlying Issues: In some cases, a persistent “not ready” status can indicate an actual problem with a monitored system, preventing the monitor from completing its test.
Getting Your Car “Ready”: The Drive Cycle
Often, the solution to “smog OBD2 not ready” is to perform a drive cycle. A drive cycle is a specific sequence of driving conditions designed to allow the OBD2 system to run all its self-tests and set the readiness monitors to “complete.” Drive cycles vary depending on the vehicle make, model, and year.
The original article mentions a Toyota MR2 drive cycle as an example. While specific drive cycles can be complex, they generally involve a combination of idling, steady speed driving at various speeds, acceleration, and deceleration.
Example (based on the provided Toyota MR2 drive cycle):
- Cold Start Idle: Start the engine when cold and let it idle for several minutes (e.g., 10 minutes).
- Highway Driving: Drive at a moderate speed (e.g., 45-55 mph) for a few minutes (e.g., 3-5 minutes), maintaining a steady engine speed.
- Idle Again: Stop and idle for a few minutes (e.g., 3-5 minutes).
- Repeat Highway and Idle: Repeat steps 2 and 3 once.
- Varied Speed Driving: Include driving at different speeds (e.g., 40-55 mph for 3 mins, then 35-45 mph for 7 mins).
- Fuel Tank Pressure Release (Specific to some vehicles): Stop, turn off the engine, and briefly release fuel tank pressure by opening and closing the fuel cap.
- More Driving: Continue with more driving at varying speeds and including stops and idles as specified in the drive cycle.
Important Considerations for Drive Cycles:
- Vehicle-Specific Procedure: Always consult your vehicle’s repair manual or search online for the specific drive cycle procedure for your make, model, and year. Generic drive cycles may not be effective.
- Safety First: Perform drive cycles in safe driving conditions, obeying all traffic laws.
- Patience: Drive cycles can take time and may need to be repeated.
- OBD2 Scanner: Using an OBD2 scanner can help you monitor the readiness status of your monitors in real-time as you perform the drive cycle, saving time and guesswork. The article links to an Autel MS309 OBD2 Scanner which is an example of a basic tool that can check readiness status.
Conclusion
“Smog OBD2 not ready” is a common issue that can usually be resolved by understanding readiness monitors and performing a proper drive cycle. By following the correct procedure for your vehicle, you can often get your car’s monitors into a “ready” state and pass your smog inspection. If the monitors remain “not ready” after several drive cycle attempts, it’s advisable to consult a qualified mechanic to diagnose any potential underlying issues that might be preventing the monitors from completing their self-tests.
