OBD2 Readiness Monitors and Emissions Tests
After battery disconnect or code clear, emissions monitors need a proper drive cycle before a smog test.
What readiness monitors are
The ECM runs self-tests for catalyst, EVAP, O2 sensors, EGR and more. Inspectors require most monitors to show “Ready.”
After clearing codes
Monitors reset to “Not Ready.” You typically need several days of mixed driving (cold start, highway, idle) for them to complete. Exact drive cycles vary by manufacturer.
Tips to pass
Fix all stored codes first. Use a scanner that shows monitor status. Avoid clearing codes the day before the test. Address EVAP and catalyst codes early — they take longer to set.
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