OBD2 Monitors Not Ready: Causes & Fixes

An OBD II “Not Ready” error message shows that the PCM (vehicle computer system) cannot check components of the emission control system.

In such a situation, the OBD scanner cannot determine if the emission control system is fully functioning or has a fault.

An emission system inspection is possible only when the tool is ready, and the PCM can check all components and report issues.

In case you are facing this problem, we have compiled this helpful guide on how to fix OBD2 Monitor Not Ready and its causes. Enjoy your reading!

What are OBD2 Monitors not Ready?

During Diagnostic scanning, a “Not Ready” message shows that your ECM has not been able to scan the emission control system correctly.

The Inspection and Maintenance feature on your OBD II works directly with the Readiness Monitor, which helps check if your vehicle is ready for an emission test.

The Readiness Monitor has a self-testing feature that helps check the condition of specific components.

The system monitors the performance of the emission system from the moment you start the car and when you are driving. A series of tests will be taking place as you drive.

Once you plug in your OBD2 scanner and click on the I/M info features, it tries to retrieve the stored data collected by the Monitors(In the form of screenshots).

As soon as the data is retrieved, you will see all the different monitors and, in front of each, their status. You will get three statuses: Okay/Ready, Not Available, and Incomplete/not Ready.

When you see a “Not Ready” status, then it means that the ECM has not had the chance to check a part or all parts of the emission system.

You should only attempt an emission test if you see Ready or Incomplete in any status. Try to get the problem solved before attempting the test.

Common causes of OBD2 Monitors not Ready

There are different causes of an OBD2 monitor not being ready, including the following.

  1. Recently disconnected battery or lost charge
  2. ECM reset with a scan tool
  3. Emission system issues
  4. Wiring issues
  5. Sensor issues
  6. Cat delete

Anything that could affect the part or the whole emission system could cause an OBD monitor not to be ready.

How to fix an OBD2 Monitors not Ready?

Before going ahead to fix your OBD2 monitor not ready issue, you need a proper diagnosis of the origin. As we know, many causes of this problem could make the fix quite tricky.

A scan tool is an excellent way to diagnose your vehicle for OBD2 monitor not ready causes properly. With this scan tool, you could get the exact component of your car causing the problem.

All you need to do is scan and check for related codes that could be traced to the emission problem. Once you can do that, you can go ahead and fix it.

Below are some of the ways you could fix an OBD2 monitor that is not ready.

1. Recently disconnected battery or lost charge fix

Many people do not know this, but whenever the ECM loses power, it automatically resets. It means whenever your battery loses charge or gets disconnected, all the data on the ECM gets wiped.

Once you disconnect your battery, data gathered by the ready monitors are automatically lost. Once you connect the OBD2 scanner and try to get that info, you will receive a “Not Ready” status.

You only need to drive your vehicle to solve this problem. By driving your car for a while, the ready monitor can gather information about the various components of the emission system. It is thanks to the multiple sensors present in these components.

2. ECM reset with a scan tool

If you reset your ECM before running the inspection and maintenance info, you might get a Not Ready from all the Ready Monitors.

Just like when you disconnect your vehicle battery, all the data gathered about the condition of the emission system is lost.

To fix this problem, you must drive your vehicle for a while to regain all the lost data.

You must avoid resetting your car’s ECM before an emission test. Doing this will prevent the experts from getting data from your ECM, which defeats the purpose of doing the test in the first place.

3. Emission system issues

Problems with the emissions could hinder the ECM from knowing the status of your vehicle. The emission system is made up of different components. All the components are equipped with sensors that monitor their activities.

Once they do not function as they should, the sensor reads it and sends the data to the ECM. It could result in a Monitor Not Ready status on the specific component.

4. Wiring issues

Every wire connects the ECM with various sensors in the vehicle. It allows the sensor to send readings on the condition of an emission system to the ECM.

Once there is a disconnection, there is no way the ECM can get information, and therefore, you get a Not Ready or Not Available status.

To solve this problem, you need to get the exact sensor with a wiring issue. Once you can get it, you must replace the wire immediately.

5. Sensor issues

The sensor plays a vital role in ensuring that the ECM gets all the information on the emission system. The ECM uses sensors like the Mass Airflow Sensor and Oxygen sensor.

Once the sensor is bad, there is no way the ECM will get data on the emission system parts. When this happens, you get a Not Ready or Not Available status.

With the help of the OBD2 scan tool, you can get the exact affected emission system component and its sensor. Find where the sensor is located and replace it with a new one.

6. Cat delete

The catalytic converter (CAT) filters exhaust gases flowing through the exhaust system. It has sensors either directly on it or closely monitoring its working condition.

When you remove the Cat, you leave ample space in the emission system, and the ECM knows the sensors. In most cases, the sensors are also removed, which is equally bad.

To solve this problem, you may need a new ECM supporting the modification. You could also use a Defouler, which tricks the ECM sensor, and the catalytic converter is present and working fine.

Final Thoughts!

Many people do not take their emissions system seriously and feel they can manage their cars with emission issues.

Significant parts of the emission, especially sensors, could affect how your engine functions.

Sensors like the O2 sensor are crucial in determining the air-fuel ratio. You must ensure they work correctly.

  • Edmond Davis

    I'm Edmond Davis, an automotive expert with years of experience in vehicle repair, performance, and safety. I graduated from the University of Michigan with a degree in Automotive Engineering and have worked with major companies like Ford, GM, and Chrysler. I'm a trusted source of information for anyone looking to learn more about cars or improve their driving experience.

    View all posts

Related Posts