After choosing ABS you have many pieces of information that are very useful in performing diagnostics. FO1 through FO8 tell you the speed of each wheel as seen by the wheel speed sensors in (mile/h) and (km/h). F09 will indicate that the brake switch has been activated by indicating a reference voltage of 5 volts which comes from the electronic control unit, not the brake switch directly. F10 is the input voltage from the G-sensor. At rest or cruising the voltage should be 2.3 volts and should decrease upon acceleration, increasing upon deceleration.
The FAO mode has nine light-emitting diodes that communicate information indicating on and off signals from the following:
• LED 2 and 7 turn on only when the valve relay is off. During normal operation the valve relay is always on.
• LED 4 represents the signal from the ABS electronic control unit to the 4EAT electronic control unit. This signal will order the transmission to go to mainly front wheel drive, shift to 3rd gear and disable the overrunning clutch (preventing engine braking).
• LED 9 monitors the electrical circuit between the ABS electronic control unit and the transmission electronic control unit. However it only performs this function while ABS is active. The wire carrying the signal for LED 9 parallels into the wire carrying the signal for LED 4.
• Mode FB1 is used to call up trouble codes.
Note: If a particular trouble code is not properly stored in memory (due to a drop in ABS Control Module power supply, etc.) when a problem occurs, the trouble code, followed by a question mark ‘’?,” appears on the Select Monitor display. This shows it may be an unreliable reading.
Mode F01 will enable you to perform a sequence control in the same manner as previously described, however the Select Monitor eliminates the need to connect terminals 3 and 6 to body ground. Follow the instructions displayed on the Select Monitor and in the service manual for performing this task. Mode FC0 is used to clear the memory.
Caution: Record all trouble codes in memory before clearing codes.
ANTILOCK BRAKE SYSTEM FOR EARLY SUBARU PART 1
ANTILOCK BRAKE SYSTEM FOR EARLY SUBARU PART 2
Antilock Brake System for Early Subaru Part 3