FAIL-SAFE FUNCTION (Light Control ECU)

WARNING: This page is about a different car, the 2003 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.

FAIL-SAFE FUNCTION (LIGHT CONTROL ECU)

When input error is inspected.

When input voltage is not within the range of operation voltage (9 to 16 V), lighting of the headlight stops. As soon as the voltage comes within the range, it lights up again.
However if the input voltage becomes low after lighting up, sufficient voltage is maintained until light of bulb completely goes off.

When output error is inspected (Open or short).
When light flushing is inspected.

When an error occurs in the output voltage (open or short) or flushing symptom occurs on the bulb, lighting of the headlight stops, the condition is maintained until power is turned ON again (headlight dimmer switch OFF --> ON).
In this case, it can not be judged whether lighting malfunction is caused by an output error or other reasons (fuse blown out, etc.).
Check that there is no error in fuse and wiring (including power source) and replace the bulb in the first place, when the error still appears, replace the light control ECU.