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.
Engine Control System (Diagnostics - Introduction) (Except For STI): General Description: Caution
- Airbag system wiring harness is routed near the ECM, main relay and fuel pump relay.CAUTION:
- Do not use electrical test equipment on the airbag system circuits.
- Be careful not to damage the airbag system wiring harness when servicing the ECM, TCM, main relay and fuel pump relay.
- Never connect the battery in reverse polarity. Doing so will damage the ECM instantly, and other parts will also be damaged.
- Do not disconnect the battery cables while the engine is running. A large counter electromotive force will be generated in the generator, and this voltage may damage electronic parts such as ECM etc.
- When disconnecting the connectors of the electrical components, always be sure to turn the ignition switch to OFF. Perform the Clear Memory Mode after connecting the connectors. Ref. to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>Clear Memory Mode .
- When measuring the voltage or resistance of individual sensor or all electrical control modules, use a tapered pin with a diameter of 0.6 mm (0.024 in) or less and touch it to the tip of terminal.
Never insert the tapered pin into the terminal because it deforms inside which may lead to a malfunction.
CAUTION: When replacing the ECM, be careful not to use the ECM of wrong specification to avoid any damage on the fuel injection system.
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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.
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