Self-Diagnostic System: OBD-II: Notes

The ECM monitors system operation using inputs from various sensors and stores Diagnostic Trouble Codes (DTCs) to aid in fault diagnosis. System requires either one or two drive cycles before a DTC is stored. With the exception of catalyst efficiency, all inputs and outputs will have been checked by the end of an appropriate drive cycle. The catalyst monitoring test requires 3 drive cycles, which include a period of steady driving.