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 an unexpected high drive voltage is detected when the
valve relay is switched to OFF. (or unexpected low voltage is detected
when the solenoid valve drive TR is switched to ON)
Item
|
Detecting
Condition
|
Possible cause
|
DTC
Strategy
|
|
|
Enable
Conditions
|
| •
|
If the valve relay is switched ON and
corrESConding solenoid driver OFF and the voltage of solenoid
< 3.5±0.5V continuously for 56ms, the failure is
detected. |
| •
|
If the valve relay is switched ON and
corrESConding solenoid driver ON and the voltage of solenoid
> 1.5±0.5V continuously for 56ms, the failure is
detected. | |
Fail
Safe
|
| •
|
The ABS/EBD/ESC functions are
inhibited. |
| •
|
The ABS/EBD/ESC warning lamps are
activated. | |
| 1. |
Connect scantool to Data Link
Connector(DLC). |
| 2. |
Ignition "ON" & Engine
"OFF". |
| 3. |
Select the "Actuation Test" mode on the
scantool. |
| 4. |
Inspect operating status of all valves with
Actuation Test.
Specification
: It's normal if operating sound is
heard.
|
|
| 5. |
Do all valves operate normally?
|
|
▶ Fault is
intermittent caused by poor connection in power harness (ABS2)
and/or HECU's connector or was repaired and HECU memory was
not cleared.
Thoroughly check
connectors for looseness, poor connection, bending, corrosion,
contamination, deterioration, or damage.
Repair or replace as necessary and then go to
"Verification Of Vehicle Repair" procedure.
|
|
|
▶ Go to
"Terminal and Connector Inspection"
procedure.
|
|
| Terminal and Connector
Inspection |
| 1. |
Many malfunctions in the electrical system are
caused by poor harness(es) and terminal condition. Faults can also
be caused by interference from other electrical systems, and
mechanical or chemical damage. |
| 2. |
Thoroughly check connectors for looseness,
poor connection, bending, corrosion, contamination, deterioration,
or damage. |
| 3. |
Has a problem been found?
|
|
▶ Repair as
necessary and then go to "Verification Of Vehicle Repair"
procedure.
|
|
|
▶
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.
|
|
| Verification of Vehicle
Repair |
After a repair, it is
essential to verify that the fault has been corrected.
| 1. |
Connect scantool and select "Diagnostic
Trouble Codes(DTCs)" mode. |
| 2. |
Using a scantool, Clear
DTC. |
| 3. |
Operate the vehicle within DTC Detecting
Condition in General Information. (Start and drive vehicle in gear
and maintain vehicle speed at or above 40kmh.
(24mph)) |
| 4. |
Using a scantool, Check DTC
present. |
| 5. |
Are any DTCs present ?
|
|
▶ Go to the
applicable troubleshooting procedure.
|
|
|
▶ System
performing to specification at this
time.
|
|
