The HECU is composed of a ECU (Electronic Control Unit ) and a HCU( Hydraulic Control Unit) , HCU is composed of a source of hydraulic pressure and modulator valve block. Increase and decrease of hydraulic pressure is opreated by electronic motor, According to a detected signal by wheel speed sensor, The hydraulic pressure which is needed for control is supplied by pump. The HCU' function which is composed of a accumulator, return pump, solenoid valve 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.
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 writed, or when the master/slave processor detects abnormal operation in RAM, Status Register, Interrupt, Timer, A/D converter or cycle time.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● Internal monitoring | ● Faulty HECU | |
Case 1 | Monitoring Period | ● Continuous | |
Enable Conditions | ● If Internal control unit failures of the master/slave processor or peripheral integrated circuits is detected. | ||
Case 2 | 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 3 s, a failure is set. | ||
Fail Safe | ● The ABS/EBD/ESP functions are inhibited. ● The ABS/EBD/ESP warning lamps are activated. | ||
Ignition "OFF".
Engine "ON".
Does warning lamp remain On?
▶ Substitute with a known-good HECU and check for proper operation. If problem is corrected, replace HECU and then go to "Verification of Vehicle Repair" procedure.
▶ Fault is intermittent caused by faulty HECU or was repaired and HECU memory was not cleared. Go to the applicable troubleshooting procedure.
After a repair, it is essential to verify that the fault has been corrected.
Connect scantool and select "Diagnostic Trouble Codes(DTCs)" mode
Using a scantool, Clear DTC.
Operate the vehicle within DTC Detecting Condition in General Information.
Are any DTCs present ?
▶ Go to the applicable troubleshooting procedure.
▶ System performing to specification at this time.
