The ABS HECU is composed of a ECU (Electronic Control Unit ) and an HCU( Hydraulic Control Unit), so the HECU hardware includes all solenoid valves inside the unit as well as the ECU. Solenoid valves are switched to ON, OFF by HECU when the ABS is activated. Solenoid valves function is to increase, decrease or maintain the hydralic pressure supplied to a wheel cylinder.
The HECU monitors the operation of the valves by checking the drive circuit of the solenid valves, and then sets this code when the unexpcted drive voltage is detected. For example, the HECU sets the DTC if the electrical feedback signal does not match the actuation signal for the corresponding valve.
Item | Detecting Condition | Possible cause | |
Case1 | DTC Strategy | ● Response monitoring | ● Faulty HECU |
Monitoring Period | ● Continuous | ||
Enable Conditions | ● The electrical feedback signal does not match the actuation signal for the corresponding valve. | ||
Fail Safe | ● ABS is switched off immediately. ● The ABS and the EBD warning lamps are activated. | ||
Case2 | DTC Strategy | ● Valve and pump motor test | |
Monitoring Period | ● The valves and Pump motor Test is performed once after ignition on if vehicle speed is >15 km/h. | ||
Enable Conditions | ● The valve and pump motor test actuates all valves in series (to detect short cuts or shunts between the valve lines). Faults are detected by monitoring the valve response signals. | ||
Fail Safe | ● ABS is switched off immediately. ● The ABS and the EBD warning lamps are activated. |
