Self-Diagnosis Function

ABS control unit has a main Central Processing Unit (CPU) and a sub-CPU that check each other and ABS system circuits. When CPUs detect a failure, ABS indicator light is turned on and a Diagnostic Trouble Code (DTC) is stored in EEPROM (nonvolatile) memory. ABS system operation is then changed to either system down or control inhibition mode as follows:

• System Down Mode: Illuminates ABS indicator light. Turns off main relay. Turns solenoid valves off. CPU operates if it has not failed. System will restart when ignition is cycled off, then on. DTC is committed to memory.
• Control Inhibition Mode: Illuminates ABS indicator light. Turns off main relay. Turns solenoid valves off. CPU operates. System will restart automatically if failure is no longer detected. DTC is committed to memory.