Encountering an “Obd Ii Monitors Not Ready” message can be frustrating, especially when you’re trying to get your vehicle to pass a smog check or emissions test. This message indicates that your vehicle’s On-Board Diagnostic system hasn’t completed its self-tests for certain emission control systems. Let’s delve into what this means and how you can address it.
OBD II monitors are diagnostic programs within your car’s computer that continuously check the functionality of various emission control systems. These monitors, such as the Catalyst Monitor and Evaporative System Monitor (Evap), ensure that components like your catalytic converter and fuel vapor recovery system are working correctly to minimize harmful emissions. When these monitors are “not ready,” it means they haven’t run and completed their diagnostic checks since the last time the vehicle’s computer memory was cleared – often due to a recent battery disconnection or fault code clearing.
Several factors can lead to OBD II monitors being in a “not ready” state. A common cause is simply disconnecting or replacing your car battery. This resets the vehicle’s computer, and the monitors need to run their tests again. Another reason could be recent diagnostic work where fault codes were cleared using a scan tool. In some cases, underlying issues with your vehicle’s emission systems might prevent the monitors from completing their cycles, though this would usually be accompanied by a check engine light and stored diagnostic trouble codes (DTCs).
To get your OBD II monitors to a “ready” status, you typically need to perform a “drive cycle.” A drive cycle is a specific set of driving conditions that prompts the vehicle’s computer to run all the necessary diagnostic tests. The exact drive cycle varies depending on the vehicle’s make, model, and engine type. For example, a Toyota MR2 with a 2AZ-FE engine might require a drive cycle like this:
A. Start the engine and let it idle for at least 10 minutes.
B. Drive at a steady speed between 43-56 mph (or higher) for 3 to 5 minutes, maintaining engine speed between 900 and 3,200 rpm.
C. Stop and idle for 3 to 5 minutes.
D. Repeat steps B and C once more.
E. Drive at 40 mph to 55 mph for 3 minutes.
F. Drive at 35 mph to 45 mph for 7 minutes.
G. Stop, turn off the engine, and release fuel tank pressure by briefly removing and reinstalling the fuel cap.
H. Restart and immediately drive at approximately 45 mph for 5 minutes.
I. Drive at around 25 mph for 15 minutes, including at least two 30-second stops.
J. Stop and idle for 2 minutes.
K. Drive at 25 mph or more for at least 50 seconds, keeping engine speed above 900 rpm.
L. Stop and idle for at least 40 seconds.
M. Repeat steps K and L ten times.
If, after performing the drive cycle, your monitors are still not ready, ensure all preconditions for the monitors to run are met (like proper fuel level, engine temperature, etc.). Then, turn the ignition off and repeat the drive cycle. If the issue persists, it might indicate a genuine problem with your vehicle’s emission system, or you may be using an incorrect drive cycle for your specific vehicle.
For more insight into your vehicle’s OBD II status, you can use an OBD II scanner. These tools, like the Autel MS309, can read diagnostic codes and display the readiness status of your monitors, saving you guesswork and time. While a drive cycle can often resolve “not ready” issues, if the monitors remain incomplete, it’s advisable to consult a qualified mechanic to diagnose and repair any underlying problems that might be preventing your vehicle from completing its self-tests and achieving a “ready” status for emissions inspections.
