1999 Lexus GS 400FACTORY OEM SERVICE PROCEDURE

Headlight Relay

Remove headlight relay (located in relay block No. 1, on right side of engine compartment, behind shock tower). Using an ohmmeter, check continuity between relay terminals. Continuity should exist between terminals No. 1 and 2. See Fig 1. Apply battery voltage and ground between terminals No. 1 and 2. Continuity should exist between terminals No. 3 and 4. If continuity is not as specified, replace headlight relay and retest system operation.

Fig 1: Identifying Headlight Relay Terminals
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.