Mitsubishi Grandis. Manual - part 479

EXPLANATION ABOUT THE MUT-III CAN BUS DIAGNOSTICS

CONTROLLER AREA NETWORK (CAN)

54D-14

2. If diagnosis code related to CAN communication 

is set as past trouble, isolate opens as described 
below.
NOTE: If you pinpoint trouble spot according to 
diagnosis code, you should use time-out 
diagnosis code. diagnosis code related to failure 
information is set when the data to be set contains 
an error, so CAN bus line itself is probably normal.

NOTE: Time-out diagnosis code codes are stored 
in each ECU memory individually. Therefore, it is 
possible that these diagnosis code codes have 
not been set simultaneously. If the trouble spot 
can not be found when you diagnose by judging 
from multiple diagnosis code codes, check the 
communication lines between each ECU.

ECU C

CAN bus line 
(g) and power 
supply system 
to ECU C

ECU C communicates with the 
MUT-III via CAN bus lines (b), (c), 
(d) and (g). The MUT-III judges 
that CAN bus lines (b), (c) and (d) 
are normal, because it can 
communicate with ECUs B and D. 
Possible trouble may be present 
in CAN bus line (g) or the power 
supply system to ECU C.

ECU C and 
ECU D

Trouble in 
CAN bus line 
(d)

ECUs C ad D communicate with 
the MUT-III via CAN bus lines (b), 
(c), (d), (e) and (g). The MUT-III 
judges that CAN bus lines (b) and 
(c) are normal, because it can 
communicate with ECU B. 
Possible trouble may be present 
in CAN bus line (d), (e) or (g) or 
the power supply system to ECU 
D. CAN bus line (d) is shared by 
ECUs C and D when they 
communicate with the MUT-III, so 
CAN bus line (d) is suspected as 
ultimate cause. CAN bus line (g) 
or (e) and power supply systems 
to ECU C or D are also suspected 
as second cause.

ECU B and 
ECU D

CAN bus line 
(e) or (f) or 
power supply 
system to ECU 
B or D

ECUs C ad D communicate with 
the MUT-III via CAN bus lines (b), 
(c), (d), (e) and (g). The MUT-III 
judges that CAN bus lines (b), (c) 
and (d) are normal, because it 
can communicate with ECU C. 
Possible trouble may be present 
in CAN bus line (f) or (e) or the 
power supply system to ECU B or 
D.

ECU which 
cannot 
communicate 
with the 
MUT-III

Possible 
trouble spot

Logic for narrowing down trouble spot

AC204742 BA

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

AC204742 BB

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

AC204742 BC

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

EXPLANATION ABOUT THE MUT-III CAN BUS DIAGNOSTICS

CONTROLLER AREA NETWORK (CAN)

54D-15

Diagnosis 
code to be set

Possible 
trouble spot

Logic for narrowing down trouble spot

Time-out 
diagnosis code 
associated with 
ECU D is stored 
in ECU A, ECU 
B and ECU C

Trouble in 
CAN bus line 
(e) and power 
supply system 
to ECU D

When time-out diagnosis code 
associated with ECU D is stored 
in ECU A, B and C, or time-out 
diagnosis code associated with 
ECUs A, B and C is stored in 
ECU D, or "bus off" diagnosis 
code is stored in ECU D, CAN 
bus line (e) is suspected. When 
diagnosis code is not stored in 
ECU D, the power supply to ECU 
D is suspected.

Time-out 
diagnosis code 
associated with 
ECUs A, B and 
C is stored in 
ECU D
"Bus off" 
diagnosis code 
is stored in ECU 
D

AC204742 BD

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

DIAGNOSIS

CONTROLLER AREA NETWORK (CAN)

54D-16

DIAGNOSIS

CAN BUS DIAGNOSTICS TABLE

M1548300200077

This diagnosis applies only to the CAN bus lines. If a 
different system is defective, proceed to the 
applicable diagnosis section for each system. 
Observe the diagnosis procedure below only when 
the CAN bus line is defective.

Time-out 
diagnosis code 
associated with 
ECU A is stored 
in ECUs B, C 
and D

Trouble in 
CAN bus line 
(a) and power 
supply system 
to ECU A

When time-out diagnosis code 
associated with ECU A is stored 
in ECUs B, C and D, or time-out 
diagnosis code associated with 
ECUs B, C and D is stored in 
ECU A, or "bus off" diagnosis 
code is stored in ECU A, CAN 
bus line (a) or (c) is suspected. 
When diagnosis code is not 
stored in ECU A, the power 
supply to ECU A is suspected.

Time-out 
diagnosis code 
associated with 
ECUs B, C and 
D is stored in 
ECU A
"Bus off" 
diagnosis code 
is stored in ECU 
A

Time-out 
diagnosis code 
codes 
associated with 
ECUs C and D 
are stored in 
ECU A and 
ECU B

Trouble in 
CAN bus line 
(d)

If time-out diagnosis code codes 
associated with ECUs C and D 
are stored in ECUs A and B, or 
time-out codes associated with 
ECUs A and B are stored in 
ECUs C and D, CAN bus line (d) 
is suspected. CAN bus line (g) or 
(e) and power supply systems to 
ECU C or D are also suspected 
as second cause.

Time-out 
diagnosis code 
codes 
associated with 
ECUs A and B 
are stored in 
ECU C and 
ECU D

Diagnosis 
code to be set

Possible 
trouble spot

Logic for narrowing down trouble spot

AC204742 BE

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

AC204742 BF

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

AC204742BG

DATA LINK 

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

DIAGNOSIS

CONTROLLER AREA NETWORK (CAN)

54D-17

CAUTION

During diagnosis, a diagnosis code associated 
with another system may be set when the 
ignition switch is turned on with connector(s) 
disconnected. After completing the repair, 
confirm all systems for diagnosis code(s). If 
diagnosis code(s) are set, erase them all.

LH DRIVE VEHICLES WITHOUT ASC