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 GS 400FACTORY OEM SERVICE PROCEDURE
Defogger Relay Circuit
- Check Rear Defogger Relay
Check rear defogger relay. See REAR WINDOW & SIDE MIRROR DEFOGGERS article. If rear defogger relay is okay, go to next step. Replace rear defogger relay as necessary. Retest system operation. - Check Circuits
Check circuits for faults between rear defogger relay and body control ECU No. 1. See WIRING DIAGRAMS. Repair or replace as necessary. If circuits are okay, go to next test listed in appropriate TROUBLE SHOOTING SYMPTOMS table.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.