On-Board Diagnostics: Notes

The On-Board Diagnostics II (OBD-II) allows for identification of malfunctions and then stores them in Engine Control Module (ECM) memory in the form of a Diagnostic Trouble Code (DTC). DTCs remain stored in memory until memory is erased. Diagnostic data including DTC information is transmitted between ECM and scan tool through the Data Link Connector (DLC). DLC is located behind cover under left side of steering column. DTC memory is part of permanent memory and is not effected by loss of voltage supply. When a DTC is stored in memory, ECM illuminates appropriate light in instrument cluster. DTCs recognized by ECM which would lead to higher emissions are indicated by Malfunction Indicator Light (MIL). DTCs recognized by ECM to be related to "E-gas" malfunctions, are indicated by Electronic Power Control (EPC) warning light.

NOTE: Malfunctions that occur intermittently are identified with the word "sporadic" on scan tool display. Stored DTCs that do not reoccur with in next 40 warm-up cycles, are automatically erased.