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.
1998 Lexus LS 400FACTORY OEM SERVICE PROCEDURE
Light Sensor Circuit
NOTE:
LEXUS scan tool must be available for this test.
- Check Light Sensor
Using scan tool, check light sensor output frequency. If light sensor frequency output is 47-1200 Hertz, go to next step. If light sensor frequency output is not 47-1200 Hertz, replace light sensor and retest system operation. - Check Circuits
Check circuits for faults between light sensor and body control ECU. See WIRING DIAGRAMS. Repair or replace as necessary. If circuits are okay, check body control ECU pin voltages. See PIN VOLTAGE TESTS. Replace as necessary and retest system operation.
Factory Service Tools
Use the Manual With the Right Hardware
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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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