The HECU consists of an ECU(Electronic Control Unit ) and a HCU(Hydraulic Control Unit). The HCU portion of the assembly contains a pump motor, solenoid valves, and accumulator. The function of the HCU is to increase, decrease or maintain the hydraulic pressure supplied to a wheel by operating the return pump according to HECU control signal while ABS control is active. The ECU monitors various sensor and switch inputs. These inputs are used to make decisions regarding HCU component operation.