DRIVE-CONTROL COMPONENTS - ABS
3-54
INITIAL CHECK FUNCTION
If it detects an error, it illuminates the warning light,
The ECU always performs an initial check on the
and disables the ABS system.
ABS system with the on-board diagnostic function.
1. Initial Check Operation
(4) If the engine starts and the ignition key is re-
(1) When the ignition key is placed in the ON posi-
turned to the “ON” position, the ABS-ECU power
tion, the power is supplied to the ABS-ECU,
supply is resumed, and initial checks in (1)
and the ABS-ECU starts a diagnostic sequence.
through (3) are performed again.
During the diagnostic period, the ABS valve
(5) When the initial checks are satisfactorily com-
relay stays in the “OFF” state and the warning
light continues to light. pleted, the ABS becomes ready for operation.
(2) Then, the ABS-ECU forces the ABS valve relay
NOTE
into the “ON” state and executes diagnostic test
An operation check for the motor relay and the motor
mode of the ABS valve relay to detect an ON
or OFF failure. is performed when the vehicle is put in motion after
(3) All the solenoid valves are caused to be ON starting the engine. This check is performed only
and OFF to make sure that the valves are not once whenever the ignition switch is turned “ON”.
sticking.
START
Ignition key ON
ACC
ABS-ECU 12v
power supply
ov . i
ABS
warning light
ABS valveON
relay
Solenoid ON
valve OFF
14X0243