Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.

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

Check the headlight control switch using the hand-held tester. Connect the hand-held tester to the DLC3. See Figure. Check the headlight control switch using DATA LIST. See INSPECTING LIGHT CONTROL SWITCH DATA LIST table. If the results are OK, perform the next test procedure of the problem symptom. See step 4 of the SYSTEM OPERATION CHECK under TROUBLE SHOOTING. If the results are not good, go to the next step.

INSPECTING LIGHT CONTROL SWITCH DATA LIST

Switch Position, Terminal (Tester Display)		Condition
OFF
Headlight Switch (Tail)		OFF
Headlight Switch (Head)		OFF
Auto Light Switch		OFF
TAIL
Headlight Switch (Tail)		ON
Headlight Switch (Head)		OFF
Auto Light Switch		OFF
HEAD
Headlight Switch (Tail)		ON
Headlight Switch (Head)		ON
Auto Light Switch		OFF
AUTO
Headlight Switch (Tail)		OFF
Headlight Switch (Head)		OFF
Auto Light Switch		ON

Check the headlight control switch. See STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. If the results are OK, go to the next step. If the results are not good, replace the headlight control switch.
Check the wiring harness and connector between the headlight control switch and body ECU. If the results are OK, perform the next test procedure of the problem symptom. See step 4 of the SYSTEM OPERATION CHECK under TROUBLE SHOOTING. If the results are not good, repair or replace the wiring harness or connector.