What is an OBD-II readiness monitor and why is it important for emissions testing?

• A. It's a manual diagnostic test run by the technician.
• B. It measures fuel pressure to determine readiness.
• C. It only indicates engine misfires.
• D. It's a self-check performed by the PCM to verify emissions control systems are functioning; monitors must be complete for pass.

Answer: (D)

An OBD-II readiness monitor is a self-check the vehicle’s PCM runs to confirm that the emissions-control systems are working properly. The PCM automatically checks multiple systems—such as the catalytic converter, EGR, EVAP, and oxygen sensors—during normal driving. When these checks complete successfully and no fault codes are present, the readiness status is marked Ready. For emissions testing, all required monitors must be complete; if any are not, the vehicle may fail the test or be considered not ready until those checks finish through proper driving cycles. This isn’t a manual test by a technician, nor is it limited to fuel pressure or engine misfires—the readiness monitoring covers the broader set of emissions-control systems.