Fail-Safe Chart

WARNING: This page is about a different car, the 2007 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.

FAIL-SAFE

Light control ECU

The light control ECU executes the fail-safe actions listed below in accordance with the item that has been detected.

FAIL-SAFE CHART

Item	Outline
Detection of Abnormal Input Voltage	If voltage that is input to light control ECU deviates from operating voltage (9 to 16 V), ECU stops illuminating headlights, and resumes illumination headlight after voltage reverts to operating voltage range. However, if input voltage decreases after headlights have illuminated, headlight will remain illuminated until bulbs are extinguished
Detection of Abnormal Output (open or short circuit) or Flashing Bulb	If abnormal condition (open or short circuit) occurs in voltage that is output by light control ECU, or if flashes bulb, ECU stops illuminating headlights and will maintain this state until power reinstated (by turning headlight control switch from ON or OFF)
Detection of Bulb Open	If bulb is not inserted in its socket, ECU stops generating high voltage until bulb is inserted correctly and power is reinstated (by turning headlight control switch from OFF to ON or turning ignition switch from OFF to ON)

Headlight beam level control system

The AFS ECU operates in the fail-safe mode if an abnormal condition such as those listed below has been detected, and illuminates the automatic headlight leveling system warning light in the combination meter.

DIAGNOSTIC CHART

Item	Abnormality Detection Condition	Description of Control
Actuator	Open or Short	Holds beam at position of actuator when abnormality has been detected
Height Control Sensor	Signal Level Abnormality	Returns beam to actuator's initial set position if abnormality has been detected higher than initial set position Holds beam at position of actuator when abnormality has been detected if abnormality is lower than initial set position
AFS ECU	When an abnormal processing of CPU has been detected	Holds beam at position of actuator when abnormality has been detected