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.
Diagnostic System
ECM of EFC system is equipped with a self-diagnostic function. When trouble occurs, ECS (Electronic Control System) light is illuminated and the trouble code is displayed on O2 monitor light. See Fig 1 .
To read trouble codes, observe oxygen sensor monitor light. This light has 2 duration periods of illumination, one period long (1.2 seconds) and one period short (.3 seconds). The long period signifies the tens digit in a numbered code. Short period signifies the ones digit. Example: 3 long flashes and 5 short flashes, would signify a code 35.
It is possible to have more than one code present. In this case, the lowest number trouble code should be diagnosed first, the next highest numbered code second and so on (sequentially). Trouble codes will be repeated as long as the system is in diagnostic mode.
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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.