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.
1993 Lexus LS 400FACTORY OEM SERVICE PROCEDURE
EFI Main Relay
- EFI main relay is located in engine compartment. Using an ohmmeter, check for continuity between relay terminals No. 1 and 3 (ES300, LS400, SC300 and SC400), or terminals No. 1 and 2 (GS300). See Fig 1 and Fig 2. Ensure continuity is not present between terminals No. 2 and 4 (ES300, LS400, SC300 and SC400), or terminals No. 3 and 5 (GS300). If continuity is not as specified, replace relay.
- Apply battery voltage between relay terminals No. 1 and 3 (ES300, LS400, SC300 and SC400), or terminals No. 1 and 2 (GS300). Using an ohmmeter, check for continuity between terminals No. 2 and 4 (ES300, LS400, SC300 and SC400), or terminals No. 3 and 5 (GS300). If continuity is not present, replace relay.
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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