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Emissions Readiness Monitors Explained

Readiness Monitors (System Checks)

1996 and newer light-duty vehicles have on board computer monitoring systems. In addition to engine management, the onboard computer also  verifies the proper function of emissions control systems by performing Emissions Control System Checks. System Checks are performed under certain driving conditions defined by the manufacturer and known as a “Drive Cycle”.  The on board computer keeps track of whether the different emissions control System Checks have been completed. Upon completion of each individual System Check, the computer flags that specific emissions control system as “READY”. If the System Check has not yet been completed, the emissions control system flags that individual System Check as NOT READY.  Readiness Monitors only confirm that the emissions control System Check has been performed; it does not test whether the system or devices within the system have passed or failed.

Readiness Monitor - "NOT READY" means the self diagnostic System Check has not completed.

Readiness Monitor - "READY" means the self diagnostic System Check has been completed.

NOTE: Regarding Vehicle Emissions Testing in Arizona, a vehicle will be rejected from emissions testing if: on 1996 - 2000 model year vehicles, more than two monitors report NOT READY; or, on 2001 or newer model year vehicles, more than one monitor reports NOT READY.