For circuit wiring diagram, see Fig 1.

NOTE: If using the hand-held tester, start the inspection from step 1 and if not using the hand-held tester, start from step 2.

Check the headlight control switch using the hand-held tester. Connect the hand-held tester to DLC3. See Figure. Check the headlight control switch using DATA LIST. See Fig 2. If the results are not OK, perform the next test procedure of the problem symptom. See BODY ECU NO. 2 PROBLEM SYMPTOM INDEX table. If the results are not OK, go to the next step.
Check the headlight control switch. See LIGHT CONTROL SWITCH article under COMPONENT TESTS in STEERING COLUMN SWITCHES. If the results are OK, go to the next step. If the results are not OK, replace the headlight control switch.
Check for short to power, short to ground and continuity in the wiring harness and connector between the headlight control switch and body ECU No. 2. If the results are OK, perform the next test procedure of the problem symptom. See BODY ECU NO. 2 PROBLEM SYMPTOM INDEX table. If the results are not OK, repair or replace the wiring harness or connector.

Fig 1: Light Control Switch Circuit Wiring Diagram

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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.

Safety Warning

Inspection Procedure