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.
2000 Lexus SC 400FACTORY OEM SERVICE PROCEDURE
Auto Set Switch Circuit
- Turn ignition off. Remove tilt and power telescopic ECU from its mounting, leaving wiring harness connector attached. turn ignition on. Measure voltage by backprobing rear of terminal No. 4 (Violet/White wire) with voltmeter positive lead and backprobing rear of terminal No. 5 (Brown wire) with negative lead at 18-pin ECU harness connector T10. See Figure. If battery voltage exists with auto set switch in on position, and voltage is less than one volt with auto set switch in off position, go to next test listed in SYMPTOM DIAGNOSIS table under TROUBLE SHOOTING. If voltage is not as specified, go to next step.
- Turn ignition off. Disconnect 18-pin tilt and power telescopic unit (combination switch) harness connector. Measure resistance between terminal No. 7 (Violet/White wire) and terminal No. 8 (Brown wire) at tilt and power telescopic unit (combination switch) harness connector. See Fig 1. With auto set switch in on position, if resistance is one megohm or more, go to next step. With auto set switch off, if continuity does not exist between terminals, replace tilt and power telescopic unit (combination switch) and retest system operation.
- Check wiring harness and connectors between tilt and power telescopic ECU and tilt and power telescopic unit (combination switch). See WIRING DIAGRAMS . Repair or replace as necessary. If wiring harness and connectors are okay, check tilt and power telescopic ECU. See TILT & TELESCOPIC ECU PIN VOLTAGE TESTS under COMPONENT TESTS. Replace tilt and power telescopic ECU as necessary and retest system operation.
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.