When you use an OBD2 code reader, the I/M Readiness indicator appears on the screen. This is a piece of cake for professionals, and they know what it means without thinking. But for us non-professionals, any small fault code will make us struggle for a long time.

So what does "I/M Readiness" that appears on the OBD2 scanner mean? What parts of our vehicle are related to it? How do we use the OBD2 diagnostic tool to check the status of I/M Readiness? Today's article will tell you the answer and help you better use the car diagnostic scanner.

What Is I/M Readiness?

I/M Readiness refers to the process of detecting whether the engine and emission control system are in normal working condition through OBDII (On-Board Diagnostics II) during regular maintenance inspection.

I/M Readiness (Inspection and Maintenance Readiness) indicates whether your car's self - diagnostic systems have finished assessing the components related to emissions. When your vehicle shows "Not Ready", it implies that certain systems have not completed their checks. As a result, the vehicle is likely to fail an emissions inspection.

Autel OBD2 reader I/M Readiness status monitoring interface

Autel OBD2 reader I/M Readiness status monitoring interface

What Systems Does I/M Readiness Monitor?

I/M Readiness involves multiple emission control components and can perform up to 11 system tests, including the following key areas:

Catalytic Converter:

The catalytic converter is the most important external purification device in the automobile exhaust system. It can convert harmful gases such as CO, HC and NOx emitted from automobile exhaust into harmless carbon dioxide, water and nitrogen through oxidation and reduction.

A "Not Ready" status may signal issues with the converter or related parts.

Oxygen Sensors:

The oxygen sensor is a device installed in the exhaust system of a car. It is mainly used to monitor the oxygen content in the exhaust gas, helping the ECU to accurately control the air-fuel ratio and ensure that the engine runs in the best working condition.

If not ready, they may be malfunctioning or unable to complete diagnostics.

Evaporative Emissions Control (EVAP):

EVAP is an environmentally friendly device used to collect fuel vapor and introduce it into the engine for combustion. Its core functions include storing fuel vapor, preventing oil and gas leakage from polluting the atmosphere, and accurately controlling the vapor recovery process through the engine control module (ECU)

"Not Ready" could point to leaks or sensor faults in the fuel system.

EVAP system affects I/M Readiness status

EVAP system affects I/M Readiness status

How to Check I/M Readiness with a Scanner

Using a diagnostic tool to check the vehicle's I/M Readiness (inspection and maintenance readiness) is a key step in evaluating whether the emission control system is operating normally. The following are the specific operating procedures and precautions:

1.Confirming the compatibility of the diagnostic tool

Make sure the scan tool supports the vehicle make and model (such as a generic OBD-II scan tool or a factory-specific tool).

Some models may require specific software versions (such as support for SAE J1979 protocol).

2.Insert the diagnostic tool and select the I/M Readiness function

Find the vehicle's OBD-II port (usually located on the lower left side of the cockpit, near the steering wheel). Plug the diagnostic tool into the port and make sure it is firmly connected.

Enter the I/M Readiness interface, find the Emission System or I/M Readiness option in the main menu, and click to enter. The diagnostic instrument will display the readiness status of each emission-related system, which is usually divided into:

Ready: The system has completed self-diagnosis and there is no fault.

Not Ready: The system has not completed self-diagnosis or there is a fault.

Incomplete: A fault has occurred recently but has not yet been confirmed (may affect emission testing).

Autel AutoLink AL519 one-click detection I/M Readiness status display

Autel AutoLink AL519 one-click detection I/M Readiness status display

Why Your Car Shows "Not Ready"

Several factors can prevent readiness monitors from completing:

Battery Disconnection: Disconnecting or resetting the battery can clear stored data, requiring the ECM to start fresh diagnostic cycles.

Short or Irregular Driving: Some monitors only run under specific conditions (e.g., cold starts, highway driving). Frequent short trips or too much idling can delay readiness.

Faulty Components: Sensors or emissions system parts may fail to complete checks due to malfunction.

Lack of Maintenance: Old spark plugs, dirty air filters, or fuel system issues can prevent the completion of readiness checks.

What Should I Do When My Car Shows Not Ready

Clear the fault code:After using the OBD2 scanner for diagnosis, perform the corresponding repair according to the fault code prompted. If you cannot handle it yourself, please go to a professional repair shop for repair. After the repair is completed, clear the fault code and re-perform the I/M Readiness status test.

Complete the OBD2 drive cycle:The reason for not being ready may be that some systems (such as catalytic converters and oxygen sensors) require specific driving conditions to complete self-diagnosis. After the driving cycle, perform the test again.This typically involves a mix of cold starts, acceleration, cruising, and idling.

Drive Under Normal Conditions: Simply driving your vehicle for a longer distance under varied conditions (city, highway, idle) can help complete the necessary drive cycles.

Why Is I/M Readiness Crucial

I/M Readiness is an important indicator for passing emissions testing. Before conducting emissions testing, it is important to check that all critical systems are "ready". If too many "not ready" are displayed, the vehicle may be rejected or directly fail the test.

Although some states allow passing the annual inspection with a "limited not ready" status, the safest way is to ensure that all systems are ready.