After codes are cleared or a battery is disconnected, supported readiness monitors may show not ready even if the warning lamp is off.
This reference supports the stated topic only. Model, model year, equipment, current rule or individual vehicle conditions may differ; check the original source before acting.
Read the California Bureau of Automotive Repair original: OBD test reference Source date: document date not recorded; research checked: 2026-11-01.
Check status, not just the lamp
Use a scanner to record supported, ready and not-ready monitors. Drive conditions and inspection allowances depend on vehicle and state rules; do not rely on a universal drive-cycle promise.
Repair before retest
Find and repair the actual cause, then verify the system under appropriate conditions. Do not clear codes just to conceal an emissions defect.
A readiness monitor reports a completed self-check
Ready does not mean every component is healthy forever; it means the supported monitor completed its check under the required conditions. Not ready can follow a battery disconnect, code clear or incomplete operating cycle. Unsupported means the vehicle does not use that monitor, and should not be counted as a failed check. Your scanner should show these states separately.
State programs differ on which model years, fuels and numbers of incomplete monitors are accepted. A universal drive-cycle recipe is unreliable because entry conditions vary by vehicle. Read the current state agency rule and ask a qualified technician about a monitor that will not complete after a proper repair.
Before a retest
- Save all stored, pending and permanent DTCs.
- Check whether the MIL is commanded on and whether supported monitors are ready.
- Confirm the underlying fault was repaired, not merely erased.
- Use the state agency's current inspection instructions for your registration location.
Sources and scope
- California Bureau of Automotive Repair — OBD test reference Document: date not recorded · Research checked: 2026-11-01
Research snapshot: 2026-11-01. Source documents may have newer revisions. Verify current instructions and VIN eligibility with the manufacturer.