Abs Control Module Section (ABSCM)

The ABSCM contains two micro control modules (MCMs) which communicate with each other. Both the MCMs process the same program and each MCM monitors the other's outputs. If a mismatch occurs between their outputs, the ABSCM cuts off the system and activate the fail-safe function.

The ABSCM can store a maximum of 3 trouble codes in an EEP ROM. If more than 3 faults have occurred, only the 3 most recent failures are stored and others are erased. Trouble codes remain stored until they are internally or externally erased.

The ABSCM has a test routine (sequence control pattern) which facilitates checking of the hydraulic control unit.

• ABS control

  Using primarily the wheel speed data from each ABS sensor and secondarily the vehicle deceleration rate data from the G sensor as parameters, the ABSCM generates a simulated vehicle speed when there is a risk of wheel lock-up. Using the simulated vehicle speed (called "dummy" vehicle speed) as a reference, the ABSCM determines the state of the wheel in terms of the tendency toward lock-up. If the result shows that the wheels are about to lock, the ABSCM issues commands to energize or de-energize the solenoid valves and activate the motor pump of the H/U to modulate 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 the rear wheel fluid pressures based on the wheel which is the most likely to lock (select-low control).

• Functions available using SUBARU select monitor

  When the SUBARU select monitor is connected, the ABSCM allows it

  • To read out analog data
  • To read out ON/OFF data
  • To read out or erase trouble code
  • To read out data showing conditions under which a trouble code has been stored (Freeze frame data)
  • To initiate ABS sequence control pattern
• Indication functions

  Under the control of the ABSCM, the ABS warning light provides the following three indication function:

  • ABS fault alerting
  • Trouble code indication (by flashing in the diagnosis mode)
  • Valve ON/OFF indication (when sequence control pattern is initiated)