Readiness monitors are self-tests the car runs to check emissions systems. A battery disconnect or code clear resets them. A smog check may reject a car whose monitors are not ready, and a drive cycle completes them.
Key takeaways
- Battery work resets monitors.
- A drive cycle completes them.
- Do not clear codes before the test.
What monitors are
The computer tests the catalyst, oxygen sensors, evap system and others on its own schedule.
What resets them
A battery disconnect, replacement, a code clear or a computer reflash.
How long it takes
Often several days of mixed driving, though some need specific conditions.
Drive cycle basics
Cold starts, steady highway driving and some stop-and-go. Specific cycles vary by car.
When to call
If monitors will not complete, a hidden fault may exist. We can check.
The monitors, one by one
A modern car runs a set of self-tests, usually the catalyst, evaporative system, oxygen sensor and its heater, and sometimes EGR and others. Each test runs only under specific conditions, such as a cold start followed by steady cruising. If conditions are never met, the monitor stays not ready. That is why a car that is mostly driven short distances in town can take longer to complete its monitors.
A realistic drive plan
Start the engine cold and let it idle briefly, then drive at moderate speeds with some stop-and-go, followed by a steady highway stretch for ten to twenty minutes. Repeat across several days. Avoid clearing codes during that period. If a single monitor refuses to complete after a week or two, bring the car in, because a hidden fault may be preventing it from running.
Need help in south Bakersfield?
Questions about smog check? Read our Smog Check page, call (661) 599-9098 or request a time. Peña's Auto Electric, Smog & Repair, 303 Taft Hwy, Suite B, Bakersfield, CA 93307. Mon to Fri 9:30 AM to 5:30 PM, Sat 8 AM to 1 PM.
Frequently asked questions
What if I replaced my battery?
Drive several days before testing.
Can I speed it up?
A proper drive cycle helps.
Will a scan show readiness?
Yes.
Why does one monitor not complete?
A fault or specific conditions.
Related reading
Sources
- California Bureau of Automotive Repair, Smog Check program and consumer information