Encountering an “Obd2 Monitors Not Ready” message during a smog or emissions test can be frustrating. It means your vehicle’s onboard diagnostic system hasn’t fully completed its self-tests, and your car might fail the inspection even if there are no obvious mechanical issues. Understanding what this means and how to address it is crucial for any car owner.
OBD2 monitors are essentially diagnostic checks that your car’s computer performs on various emission control systems. These monitors, such as the Catalyst Monitor and Evaporative System Monitor, run tests to ensure these systems are functioning correctly and minimizing harmful emissions. When these monitors are “ready,” it signifies that these tests are complete and passed. However, if they are “not ready,” it indicates that these tests are either incomplete or have not yet run since the last time the car’s computer system was reset or the battery was disconnected.
Several reasons can cause OBD2 monitors to be in a “not ready” state. Common scenarios include:
- Recent Battery Disconnection or Replacement: Disconnecting the car battery for maintenance or replacement will reset the OBD2 system and erase the monitor status.
- Clearing Diagnostic Trouble Codes (DTCs): Using an OBD2 scanner to clear fault codes also resets the monitors.
- Recent Repairs: After certain repairs, particularly those related to the emission system, the monitors might reset and need to run again to confirm the fix.
- Interrupted Drive Cycles: Monitors often require specific driving conditions, known as “drive cycles,” to run and complete their tests. If these drive cycles are interrupted or not fully executed, monitors may remain “not ready.”
To get your OBD2 monitors to a “ready” status, especially if you need to pass an emissions test, performing a drive cycle is often necessary. A drive cycle is a specific set of driving conditions that prompts the car’s computer to run all the required OBD2 monitor tests. Drive cycles are manufacturer-specific and can vary significantly between car makes and models.
For example, a Toyota MR2 (Engine Class 2AZ-FE) drive cycle might involve steps like this:
A. Start the engine and allow it to idle for 10 minutes or more.
B. Drive the vehicle at 43-56 mph or more for 3 to 5 minutes, maintaining engine speed between 900 and 3,200 rpm.
C. Stop the vehicle and allow the engine to idle for 3 to 5 minutes.
D. Repeat steps B and C once.
E. Drive the vehicle at 40 mph to 55 mph for 3 minutes.
F. Drive the vehicle 35 mph to 45 mph for 7 minutes.
G. Stop the vehicle and turn off the engine. Release fuel tank pressure by removing and reinstalling the fuel tank cap.
H. Start the engine and drive at approximately 45 mph for 5 minutes as soon as it is safe to do so.
I. Drive the vehicle at approximately 25 mph for 15 minutes, including at least two stops for about 30 seconds each.
J. Stop the vehicle and allow the engine to idle for 2 minutes.
K. Drive the vehicle at 25 mph or more for at least 50 seconds, ensuring engine speed is above 900 rpm.
L. Stop the vehicle and allow the engine to idle for 40 seconds or more.
M. Repeat steps “K” and “L” ten times.
It’s important to note that this is just one example, and your vehicle might require a different drive cycle. Consult your vehicle’s repair manual or search online for the specific drive cycle for your car’s make, model, and year.
After performing a drive cycle, you can check the status of your OBD2 monitors using an OBD2 scanner. A basic scanner, like the Autel MS309, can read OBD2 data and show you whether the monitors are ready or not. This can save you a trip to the smog check station only to find out your car is still not ready.
If, after performing the correct drive cycle multiple times, your OBD2 monitors still show as “not ready,” there might be an underlying issue preventing the monitors from completing. In such cases, it’s advisable to seek professional diagnosis from a qualified mechanic. There could be a fault code that hasn’t triggered the check engine light but is still preventing monitor readiness, or there might be a genuine issue with one of the emission control systems.
Getting your OBD2 monitors to a “ready” status is a necessary step for passing emissions tests. Understanding the process and utilizing drive cycles and OBD2 scanners can help you troubleshoot and resolve this issue effectively. If you’re still facing problems, professional help is always available to ensure your vehicle is running correctly and meeting emission standards.
