Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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 | Diagnostic service | ||
|---|---|---|---|
| Diagnostic Trouble Code (DTC) | Service $03 of SAE J1979/ISO 15031-5 | ||
| Freeze Frame data | Service $02 of SAE J1979/ISO 15031-5 | ||
| System Readiness Test (SRT) code | Service $01 of SAE J1979/ISO 15031-5 | ||
| 1st trip Diagnostic Trouble Code (1st Trip DTC) | Service $07 of SAE J1979/ISO 15031-5 | ||
| 1st trip Freeze Frame data | - | ||
| Test values and Test limits | Service $06 of SAE J1979/ISO 15031-5 | ||
| Calibration ID | Service $09 of SAE J1979/ISO 15031-5 | ||
| Permanent Diagnostic Trouble Code (Permanent DTC) | Service $0A(1) of SAE J1979/ISO 15031-5 | ||
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The above information can be checked using procedures listed in the table below.
| x: Applicable -: Not applicable | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| DTC | 1st trip DTC | Freeze Frame data | 1st trip Freeze Frame data | SRT code | SRT status | Test value | Permanent DTC status | |||
| CONSULT-III | x | x | x | x | x | x | - | x | ||
| GST | x | x | x | - | x | x | x | x | ||
| ECM | x | x(1) | - | - | - | x | - | - | ||
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The malfunction indicator lamp (MIL) on the instrument panel illuminates 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 ".)
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.