Fail-Safe Chart

WARNING: This page is about a different car, the 2006 Lexus IS 350 and 2006 Lexus IS 250. 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.

ITEM OUTLINE

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 illuminating headlight once the voltage reverts to the operating voltage range However, if input voltage decreases after headlights have illuminated, headlight will remain illuminated until the 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 bulb flashes, ECU stops illuminating headlights and will maintain this state until power is 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 engine switch from off to on (IG))

AFS ECU

HINT:

If a malfunction is detected, the headlight swivel ECU assembly (AFS ECU) performs fail-safe operation. Depending on the malfunction, the ECU flashes at 1 Hz intervals or illuminates the AFS OFF indicator in the combination meter assembly. Warning massages are also shown on the multi-information display.

AFS ECU ITEM

Item	Detection Condition	Leveling motor control	Swivel motor control	Operation restore condition	Indicator
Swivel motor (motor)	Open Short Overheat	Continues with the right and left leveling motor positions lowered by 0.8° from the current position.	The normal swivel motor returns to the front position. The abnormal swivel motor stops at the current position.	IG ON cycled	Blinks
	Gear malfunction			IG ON cycled Position change is detected
	Stop position error			IG ON cycled Normal stop position is detected
Swivel motor (sensor)	Open Short	Continues	Returns to the front position.	IG ON cycled Normal stop position is detected	Blinks
Steering angle sensor	Trouble information is received Communication error	Continues with the right and left leveling motors lowered from the current position by 0.8°. Continues after the swivel motor returns to the front position.	Stops at the current position and then returns to the front position.	IG ON cycled Normal stop position is detected	Blinks
Speed sensor	Open Short	Continues using the normal vehicle speed signal that is supplied by the skid control ECU if one sensor is malfunctioning. Continues determining that the vehicle is stationary if both sensors are malfunctioning.	If one sensor is malfunctioning, the swivel motor is controlled using the normal vehicle speed signal that is supplied by the skid control ECU, and the motor returns to the front position. If both sensors are malfunctioning, the motor returns to the front position.	IG ON cycled	Blinks
Height control sensor	Open Short Pitch angle error Power source trouble	If the height position is higher than the initial position, the leveling motor is returned to the initial position. If the leveling motor position is lower than its initial position, the leveling motor stays at the current position.	Returns to the front position.	IG ON cycled Normal stop position is detected	Blinks
Leveling motor	Open Short Overheat	The abnormal leveling motor stops at the current position. The normal leveling motor returns to its initial position if its current position is higher than the initial position. The normal leveling motor will stop at the current position if this position is lower than the initial position.	Returns to the front position.	IG ON cycled	Blinks
BEAN communication	Interruption of headlight signal communication Interruption of headlight signal from the Windshield Wiper Switch assembly Interruption of steering sensor zero-point signal Interruption of front wheel speed signal communication	Continues	Returns to the front position.	Signal is no longer interrupted.	Blinks
	Interruption of AFS OFF switch signal		Returns to the front position.		Illuminates
	Interruption of engine speed signal communication Interruption of vehicle speed communication		Continues		Blinks
AFS ECU	ECU internal malfunction	Continues	Continues	IG ON cycled	Goes off
Wheel speed data error	Abnormal front wheel speed signal is received from the skid control ECU	Continues	Returns to the front position.	Normal signal is received	Blinks