The HECU send
requirement data, such as Torque reduction, the number of fuel cut
cylinders, and ESC control requests, to the Engine PCM(ECM & TCM)
through CAN bus line.
The Engine PCM(ECM)
performs fuel cut functions according to requests from the HECU and
retards ignition timing by torque reduction requests.
The PCM(TCM) maintains
current gear positions during ESC control time, in order not to increase
power which causes a Kickdown shift.
The HECU checks the CAN
communication lines for normal TCS control, and sets this code if CAN BUS
OFF status is detected for more than 100ms.
Item
|
Detecting
Condition
|
Possible cause
|
DTC
Strategy
|
| •
|
Open or short circuit
monitoring | |
| •
|
Open or short circuit in CAN
line |
|
Enable
Conditions
|
| •
|
In case CAN BUS off state continued for
more than 100ms. | |
Fail
Safe
|
| •
|
Inhibit the ESC control and allow the
ABS/EBD control. |
| •
|
The ESC warning lamp is
activated. | |
| 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.
|
|
|
▶ Go to
"CAN Signal Circuit Inspection"
procedure.
|
|
| CAN Signal Circuit
inspection |
Short Check (to ground)
| 1. |
Ignition "OFF" & Engine
"OFF". |
| 2. |
Disconnect the HECU
connector. |
| 3. |
Measure resistance between CAN LOW terminal,
CAN HIGH terminal of the HECU harness connector and chassis
ground.
|
| 4. |
Is the measured value within
specifications?
|
|
▶ Go to
next procedure.
|
|
|
▶ If
abnormal resistance is detected in CAN HIGH circuit, Repair
short to ground in CAN HIGH circuit and then go to
"Verification Of Vehicle Repair" procedure.
▶ If abnormal resistance is detected in CAN LOW
circuit, Repair short to ground in CAN LOW circuit and then go
to "Verification Of Vehicle Repair"
procedure.
|
|
CAN BUS Resistance Check
| 1. |
Ignition "OFF" & Engine
"OFF". |
| 2. |
Disconnect the HECU
connector. |
| 3. |
Measure resistance between CAN LOW terminal
and CAN HIGH terminal of the HECU harness connector.
Specification
: Approx. 60Ω
| |
| 4. |
Is the measured value within
specifications?
|
|
▶ Go to
"Component Inspection" procedure.
|
|
|
▶ In case
of the resistance "approx. 1Ω" : Repair mutual short in CAN
signal circuit of the HECU and then go to "Verification Of
Vehicle Repair" procedure.
▶ In
case of the resistance "∞ Ω" : Repair open in CAN signal
circuit of the HECU and then go to "Verification Of Vehicle
Repair" procedure.
▶ In case of the
resistance "approx. 120 Ω" : Check the resistances(122Ω) in
I/P junction box and ECM, repair as necessary and then go to
"Verification Of Vehicle Repair"
procedure.
|
|
| Component Circuit
Inspection |
| 2. |
Ignition "ON" & Engine
"OFF". |
| 3. |
Connect scantool and select "Diagnostic
Trouble Codes(DTCs)" mode. |
| 4. |
Using a scantool, Clear
DTC. |
| 5. |
Select "Diagnostic Trouble Codes(DTCs)" mode
again. |
| 6. |
Are any DTCs present ?
|
|
▶
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 poor connection in CAN signal harness
and/or HECU's connector.
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. |
| 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.
|
|
