Impreza RS Coupe AWD F4-2.5L SOHC (1999)
Electronic Brake Control Module: Description and Operation
The ABSCM is a digital control type electronic control module accommodating two Micro-control Modules (MCMs); master and slave. Both MCMs
process the same program and monitor the respective outputs, and when a mismatch occurs, cut off the system to activate the fail-safe function.
A maximum of 3 trouble codes are stored in the EEPROM and if 3 or more areas fail, then only the 3 most recent failures are stored. The trouble codes
remain stored until they are erased.
This ABSCM induces a sequence control pattern and facilitates the checking of the hydraulic unit.
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ABS control
Based on the four wheel speed signals, the ABSCM calculates a simulated body speed or body deceleration rate, while referencing the G sensor
output as an auxiliary means, and compares them with the wheel speeds and wheel deceleration rates. If it determines that the wheels are about to
lock, it controls the solenoid.valve or motor pump of the H/U to adjust the brake fluid pressures that act on the wheel cylinders, thereby preventing
the wheels from locking.
The ABSCM controls the right and left front wheel fluid pressures independently and controls the rear wheel fluid pressures on the basis of the
wheel which is more likely to lock (Select-low control).
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Select monitor associated functions
The Subaru select monitor may be used to perform the following operations.
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To read out analog data
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To read out ON/OFF data
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To read out or erase trouble code
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To read out status information in the event of trouble (Freeze frame data)
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To initiate ABS sequence control pattern
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Indication functions
The ABS warning light can be made to indicate the following three states.
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ABS trouble
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Flashes to indicate trouble codes in diagnosis mode.
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Valve ON/OFF when sequence control pattern is in effect
