Main Control
The ABS control unit detects the wheel speed based on the wheel sensor signal it received, then it calculates the vehicle speed based on the detected wheel speed. The control unit detects the vehicle speed during deceleration based on the rate of deceleration.
The ABS control unit calculates the slip rate of each wheel, and it transmits the control signal to the modulator unit solenoid valve when the slip rate is high.
The pressure reduction control is a three-mode system, that is pressure reduction, pressure retaining and pressure intensifying modes.
Self-diagnosis Function
The ABS control unit is equipped with a main CPU and a sub CPU, and the CPUs check each other.
The CPUs check the circuit of the system.
When the CPUs detect failure, they shift to the "system down mode" or the "control inhibition mode".
| MODE | ABS INDICATOR LIGHT | MAIN RELAY | SOLENOID VALVE | CPU | Restart condition | DTC | |||
|---|---|---|---|---|---|---|---|---|---|
| SYSTEM DOWN | ON | No operation | Drive inhibition | Operation(1) | Ignition switch | OFF → ON (II) | Memory | ||
| CONTROL INHIBITION | ON | No operation | Drive inhibition | Operation | Automatic | Memory | |||
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The self-diagnosis can be classified into these four categories.
(1): Initial diagnosis
(2): Except ABS control
(3): During ABS control
(4): During warning