Accord LX Sedan L4-2156cc 2.2L SOHC MFI (1997)
ABS Control Unit: Description and Operation
Diagnosis Function
ABS Indicator Light
ABNORMALITY DETECTION
The Anti-lock Brake System (ABS) control unit turns the ABS indicator light on when one or more of the following abnormalities are detected.
This is only a partial list.
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When the operating time of the motor in the power unit exceeds the specified period.
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When vehicle running time exceeds 30 seconds without releasing the parking brake.
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When absence of speed signals from any of the four wheel sensor is detected.
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When the activation time of all solenoids exceeds a given time, or an open circuit is detected in the solenoid system.
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When solenoid output is not detected in the simulated ABS operation when the engine is started or the vehicle is driven.
BULB CHECK
To check the indicator light bulb, the light is activated when the ignition switch is first turned on. The light goes off after the engine is started if
there is no abnormality in the system.
Fail Safe
FUNCTION
When an abnormality is detected in the ABS control system self-diagnosis, the solenoid operations are suspended by turning off the two fail-safe
relays. This disconnects the ground circuits of all the solenoid valves to prevent ABS operation.Under these conditions, the braking system
functions just as an ordinary one.
RELAY
The fail-safe relay's terminal side contact is normally open. When there is continuity at the relay coil, the fail-safe relay is closed, thereby
connecting the ground circuit to the solenoid valve.
Pump Motor Control
The ABS control unit monitors the brake fluid pressure in the accumulator by the pressure switch ON/OFF signals. The ABS control unit turns the pump
on when the pressure in the accumulator drops, and stops the pump when the pressure rises to the specified value. If the pressure does not reach the
specified value after the motor has operated continuously for a specified period, the ABS control unit stops the motor and activates the ABS indicator
light.
Self-Diagnosis
PURPOSE
The self-diagnosis function, provided in the sub function of the Anti-Lock Brake Sysytem (ABS) control unit, monitors the main system functions
by constantly transmitting the data between the two Central Processing Units (CPU).
FUNCTION
When an abnormality is detected, the ABS control unit turns the ABS indicator light on and stops the ABS, although the basic brake system
continues to operate normally. When the ABS control unit detects an abnormality with the ABS and turns the ABS indicator light on, the
Diagnostic Trouble Code (DTC), which shows the problem part or unit, is recorded in the control unit. The DTC can be read by the blinking
frequency of the ABS indicator light.
