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.
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HOMESERVICE MANUALSLEXUS1999RX 300 AWD V6-3.0L (1MZ-FE)REPAIR AND DIAGNOSISBODY AND FRAMEBODY CONTROL SYSTEMSBODY CONTROL MODULETESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSHEADLIGHT RELAY CIRCUIT
1999 Lexus RX 300 AWD V6-3.0L (1MZ-FE)
Headlight Relay Circuit
1999 Lexus RX 300 AWD V6-3.0L (1MZ-FE)SECTION Headlight Relay Circuit
CIRCUIT DESCRIPTION
Head light relay will be "ON" by operating the headlight switch. The transistor which activates the taillight relay has two sorts: one activates directly by the headlight switch for fail safe and the other activates by CPU. the one that activates by CPU has two systems and prevents the headlight from turning off at the time of one system trouble in the automatic operation circuit.

WIRING DIAGRAM

INSPECTION PROCEDURE
HINT: In case of using the LEXUS hand-held tester,start the inspection from step 1 and in case of not using the LEXUS hand-held tester, start from step 2.
Head light relay will be "ON" by operating the headlight switch. The transistor which activates the taillight relay has two sorts: one activates directly by the headlight switch for fail safe and the other activates by CPU. the one that activates by CPU has two systems and prevents the headlight from turning off at the time of one system trouble in the automatic operation circuit.
WIRING DIAGRAM
Step 1:
Step 2:
Step 3:
INSPECTION PROCEDURE
HINT: In case of using the LEXUS hand-held tester,start the inspection from step 1 and in case of not using the LEXUS hand-held tester, start from step 2.
RENDER: 1.0x
NO RELATED
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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.