Component Location
General Description
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.
Increase and decrease of hydraulic pressure is opreated by electronic motor, according to a measured signal by wheel speed sensor.
The function of HCU is to increase, decrease or maintain the hydralic pressure supplied to a wheel cylinder by operating 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.
DTC Description
The HECU monitors the operation of the IC components such as memory, register, A/D converter and so on.
The ECU sets this code when the EEPROM data read by the master processor is different than prior data written, or when the master/slave processor detects abnormal operation in RAM, Status Register, Interrupt, Timer, A/D converter or cycle time.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | Internal monitoring
| Faulty HECU
|
Case1 | Monitoring Period | Continuous
|
Enable Conditions | If Internal control unit failures of the master/slave processor or peripheral integrated circuits is detected.
|
Case2 | Monitoring Period | Directly after ignition on, during reading of EEPROM-values
|
Enable Conditions | Failure is set if checksum not correct or PSW-EEPROM-Handler reported unknown failure during EEPROM-value reading. If EEPROM reading sequence take longer then 3s, a failure is set.
|
Fail-Safe | The ABS/EBD/ESP functions are inhibited. The ABS/EBD/ESP warning lamps are activated.
|
Diagnostic Circuit Diagram