Headlights - Automatic: Other Lexus SC I

LIGHT SENSOR

Note. Adjust light sensor if headlights come on too early or too late.

If headlights come on too early, turn ring on light sensor counterclockwise. (Scheme 2) If headlights come on too late, turn ring clockwise.

Scheme 2

Integration Relay Circuit (At Junction Block)

Turn ignition off. Disconnect harness connector from integration relay. Remove integration relay. Check continuity between chassis ground and following junction block connector terminals, where integration relay was installed. (Scheme 3) If continuity is as specified, perform circuit voltage test. See VOLTAGE TESTS.

1. Terminal No. 4 - With passenger's door closed (door courtesy switch contacts open), there should be no continuity. With passenger's door open (door courtesy switch contacts closed), there should be continuity.
2. Terminal No. 5 - With key removed from ignition switch, there should be no continuity. With key inserted into ignition switch, there should be continuity.
3. Terminal No. 6 - With driver's door closed (door courtesy switch contacts open), there should be no continuity. With driver's door open (door courtesy switch contacts closed), there should be continuity.
4. Terminal No. 8 - With seat belt buckled, there should be no continuity. With seat belt unbuckled, there should be continuity.
5. Terminal No. 10 - There should be continuity at all times.

Light Sensor Circuit

Turn ignition off. Disconnect light sensor connector. Check for continuity between chassis ground and following light sensor harness connector terminals. (Scheme 5) If continuity is as specified, perform circuit voltage test. See VOLTAGE TESTS.

1. Terminal No. 3 - With driver's door closed (door courtesy switch contacts open), there should be no continuity. With driver's door open (door courtesy switch contacts closed), there should be continuity.
2. Terminal No. 4 - With headlight switch in any position except AUTO, there should be no continuity. With headlight switch in AUTO position, there should be continuity.

Integration Relay Circuit

Turn ignition off. Disconnect harness connector from integration relay. Remove integration relay. Check voltage between chassis ground and following junction block connector terminals, where integration relay was installed. (Scheme 3) If voltage is as specified, integration relay may be faulty.

1. Terminals No. 1 & 2 - Battery voltage (or slightly less) should be present at all times.
2. Terminals No. 7, 9 & 11 - With ignition switch in LOCK or ACC position, no voltage should be present. With ignition switch in ON position, battery voltage should be present.

Disconnect light sensor connector. Check voltage between chassis ground and following light sensor harness connector terminals. (Scheme 5) If voltage is as specified, light sensor may be faulty.

1. Terminal No. 1 - With ignition switch in LOCK or ACC position, no voltage should be present. With ignition switch in ON position, battery voltage should be present.
2. Terminal No. 2 - Battery voltage should be present at all times.

Scheme 3

Scheme 4

Scheme 5