Management Of Failure Detection

When HECU detects malfunction in ABS, it enters fail-safe mode and HECU manages ABS as follows:

1. When ABS goes down, ABS and EBD functions are inhibited and ABS and EBD warning lights are activated. When this happens, ABS valve relay and all solenoids are prevented from being switched on.
2. During functions where only ABS function is inhibited, ABS warning light is activated and EBD warning lamp is not activated.
3. Sensor failure outside ABS control cycle:
   • If only one wheel fails, only ABS is inhibited.
   • When more than two wheels fail at same time, ABS and EBD are inhibited.
4. Sensor failure inside ABS control cycle:
   • If one front wheel fails, HECU inhibits ABS control of failed-wheel and maintains ABS control of other wheels. After the controller completes the ABS control, only ABS is inhibited and ABS warning light is activated.
   • If one rear wheel fails, HECU inhibits ABS control of both front wheels and pressure of both rear wheels is decreased. After controller completes ABS control, only ABS is inhibited and ABS warning light is activated.
   • If more than two wheel failures, ABS and EBD functions are inhibited and ABS and EBD warning lights are activated.
5. Low operating voltage is detected by HECU:
   • When outside ABS control cycle, HECU inhibits ABS control of front wheels and allows ABS control of rear wheels, by deactivating appropriate motor. ABS warning light is illuminated immediately. When voltage is returned to the normal operating range, HECU enables ABS functions and ABS warning light is switched off and erases low voltage DTC.
   • When inside ABS control cycle, HECU inhibits ABS control of front wheels and allows ABS control of rear wheels, by deactivating ABS motor. ABS warning light is illuminated immediately and remains on. DTC is stored in memory.
6. During ABS motor failure, HECU inhibits ABS control of front wheels but allows ABS control of rear wheels, by deactivating motor. After ABS controller completes the ABS control, only ABS is inhibited and ABS warning light is activated.