Self-Diagnostic 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 (non-volatile) memory. Self-diagnosis can be classified into detection timing categories:

• Initial diagnosis: Performed right after engine starts and until ABS indicator goes off.
• Regulator diagnosis: Performed right after initial diagnosis and until ignition switch is turned off.

When a problem is detected by self-diagnosis function, system will turn ABS fail-safe relay, solenoid valve and pump motor off, and will turn ABS indicator light on.