The OBD System Check Determines:
- If Malfunction Indicator Light (MIL) works.
- If PCM/VCM is operating and can recognize a fault.
- If any Diagnostic Trouble Codes (DTCs) are stored.
After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the OBD system circuit check, if no codes are indicated and driveability problems still exist, see TESTS W/O CODES article and SCAN TESTER usage in TESTS W/CODES article.
- Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to A-1, MALFUNCTION INDICATOR LIGHT (MIL) .
- Turn ignition off. Install Tech 1 scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to A-2, NO SCAN TOOL DATA.
- If DTC(s) are present, go to step 6). If DTC(s) are not present, go to next step.
- Attempt to start engine. If engine start and runs, go to next step. If engine does not start or starts and dies, go to A-3, NO-START DIAGNOSIS .
- Compare scan tool engine data with actual control system data values. If parameter is within limits, go to step 7). If parameter is not within limits, go to step 8).
- Diagnose DTC(s) using appropriate self-diagnostic test. See TESTS W/CODES article.
- See TESTS W/O CODES article.
- See SYSTEM/COMPONENT TESTS article.