OBD Readiness: Ready, Not Ready, Not Supported

A vehicle's OBD-II system runs onboard self-tests to check emissions-related systems and components. Scan tools often list the test results under I/M Readiness, Monitor Status, or a similar label. The main purpose of the readiness display is to indicate whether a monitor's required diagnostic self-test has completed; that is separate from whether the ECU has detected a trouble code. 1

Ready

For a supported monitor, Ready (sometimes displayed as Complete) means its required self-test reported completion at the time and within the reporting window of the reading. Ready is good evidence about completion, but is not a guarantee that every part is healthy or that the vehicle has passed a government emissions inspection. Other data such as MIL, faults and vehicle/program exceptions may matter. 1 2 2

Not Ready / Incomplete

For a supported monitor, Not Ready (Incomplete) means the required self-test has not reported completion. The monitor may have been reset by a battery disconnect or code clear, or the necessary enabling conditions may not have occurred. An incomplete EVAP monitor does not establish a bad EVAP valve; an incomplete Catalyst monitor does not establish a failed catalytic converter. Further evidence is required. 1 1 1

Not Supported

Not Supported means the diagnostic system says that particular monitor is not supported or not applicable. It is not a failed/incomplete test. Scanners sometimes display a long universal monitor list; a vehicle is not required to support every monitor in that list. Do not include explicitly Not Supported monitors in an incomplete count.

Unknown

If a tool fails to show a monitor or you do not know which status it reported, Unknown is the honest option. The absence of a result is not proof of completion, non-support or a fault. A good diagnostic record keeps unknown states visible and tells you what to recheck.

Since Codes Were Cleared vs This Drive Cycle

Some scanners expose different windows of readiness data. Since DTCs were cleared covers the period following relevant diagnostic reset, and is the better foundation for longitudinal readiness tracking. This drive cycle asks what happened during a more limited operating period; the two are not equivalent. If two readings use different windows, do not conclude a monitor has gotten better or worse merely because the displays differ. 3

Continuous and Non-continuous Monitors

Certain checks run frequently or continuously during appropriate operation; others need specific prerequisites before they can execute. Manufacturer and control-system differences matter. A generic list of names cannot tell you which tests your particular engine has completed without a genuine scan. 1

What Should You Record?

Capture the date, scanner name if known, reporting horizon, each supported monitor state, MIL, whether you checked confirmed/pending codes, and recent power or code-clearing events. A photographed inspection sheet or scan report can be a good reference, but this tool uses manual entry instead of OCR or direct hardware access.

Record your scanner observations.