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Code Enable Criteria

Engine speed is 1500-3000 RPM.
Loop status is closed.
Calculated airflow is greater than 7 grams per second.
No CAM, CKP, ECT, EGR, EVAP purge solenoid, fuel trim, IAT, MAP, misfire, O2S1 or TP sensor DTCs are set.

DTC sets if ratio of O2S1 lean-to-rich average time to rich-to-lean average time is not 0.6-2.8 within a 100 second test.