On Board Diagnostic (OBD) System: Introduction
The ECM has an on board diagnostic system, which detects malfunctions related to engine sensors or actuators. The ECM also records various emission-related diagnostic information including:
EMISSION-RELATED DIAGNOSTIC INFORMATION AND SAE MODE
| Emission-related diagnostic information | SAE Mode |
|---|---|
| Diagnostic Trouble Code (DTC) | Mode 3 of SAE J1979 |
| Freeze Frame data | Mode 2 of SAE J1979 |
| System Readiness Test (SRT) code | Mode 1 of SAE J1979 |
| 1st Trip Diagnostic Trouble Code (1st Trip DTC) | Mode 7 of SAE J1979 |
| 1st Trip Freeze Frame data | - |
| Test values and Test limits | Mode 6 of SAE J1979 |
| Calibration ID | Mode 9 of SAE J 1979 |
NOTE:
The above information can be checked using procedures listed in the table below.
TESTING PROCEDURES
| - | DTC | 1st trip DTC | Freeze Frame data | 1st trip Freeze Frame data | SRT code | Test value | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| CONSULT-II | X | X | X | X | X | - | ||||
| GST | X | X | X | - | X | X | ||||
| ECM | X | X(1) | - | - | - | - | ||||
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The malfunction indicator lamp (MIL) on the instrument panel lights up when the same malfunction is detected in two consecutive trips (Two trip detection logic), or when the ECM enters fail-safe mode. (Refer to FAIL-SAFE CHART .)