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.
1999 Hyundai Sonata GLS, AutomaticFACTORY OEM SERVICE PROCEDURE
Ground Circuits
- Turn ignition off. Check resistance between chassis ground and ECM ground terminals. See ECM GROUND TERMINAL IDENTIFICATION table. If less than 2 ohms exists, go to next step. If more than 2 ohms exists, repair wire(s) between ECM and ground.
- Connect voltmeter negative lead to chassis ground. Connect positive lead to each ECM ground terminal. See ECM GROUND TERMINAL IDENTIFICATION table. With engine running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, corrosion or loose connection in ground circuit.
Factory Service Tools
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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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