Mitsubishi Lancer (4A9 engine). Manual — part 247

EXPLANATION ABOUT THE M.U.T.-III CAN BUS DIAGNOSTICS

CONTROLLER AREA NETWORK (CAN)

54C-12

ECU which
cannot
communicate
with the
M.U.T.-III

Possible
trouble spot

Logic for narrowing down trouble spot

ETACS-ECU
and all ECUs

CAN bus line
(h) and power
supply system
to ETACS-
ECU

The ETACS-ECU and the other
ECUs use the CAN bus line (h)
when they communicate with the
M.U.T.-III. Since none of the
ETACS-ECU and the other ECUs
can communicate with the
M.U.T.-III, CAN bus line (h) or the
power supply circuit to the
ETACS-ECU may be faulty.

AC204742BO

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

ECU A

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

ECU A communicates with the
M.U.T.-III via CAN bus lines (a)
and (b). The M.U.T.-III judges that
CAN bus line (b) is normal,
because it can communicate with
other ECUs. Possible trouble may
be present in CAN bus line (a) or
the power supply system to ECU
A.

AC204742BH

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

ECU C

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

ECU C communicates with the
M.U.T.-III via CAN bus lines (b),
(c), (d) and (g). The M.U.T.-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.

AC204742BI

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

EXPLANATION ABOUT THE M.U.T.-III CAN BUS DIAGNOSTICS

CONTROLLER AREA NETWORK (CAN)

54C-13

2. Pinpoint possible trouble spot according to

diagnosis code
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 diagno-
sis code. diagnosis code related to failure infor-
mation is set when the data to be set contains an
error, so CAN bus line itself is probably normal.

ECU C and
ECU D

Trouble in
CAN bus line
(d)

ECUs C and D communicate with
the M.U.T.-III via CAN bus lines
(b), (c), (d), (e) and (g). The
M.U.T.-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 or C. CAN bus line (d) is
shared by ECUs C and D when
they communicate with the
M.U.T.-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.

AC204742BJ

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

ECU B and
ECU D

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

ECUs B and D communicate with
the M.U.T.-III via CAN bus lines
(b), (c), (d), (e) and (f). The
M.U.T.-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.

AC204742BK

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

All ECU (except
ETACS-ECU)

CAN bus line
(b)

The other ECUs except the
ETACS-ECU use CAN bus lines
(b) and (h) when they
communicate with the M.U.T.-III.
It must be assumed that CAN bus
line (b) is defective since the
ETACS-ECU can communicate
with the M.U.T.-III.

AC204742BP

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

ECU which
cannot
communicate
with the
M.U.T.-III

Possible
trouble spot

Logic for narrowing down trouble spot

EXPLANATION ABOUT THE M.U.T.-III CAN BUS DIAGNOSTICS

CONTROLLER AREA NETWORK (CAN)

54C-14

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
cannot be found when you diagnose by judging
from multiple diagnosis code codes, check the
communication lines between each ECU.

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 codes associated with
ECUs A, B and C are 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.

AC204742BL

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

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

Trouble in
CAN bus line
(a) or (c) 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 codes associated with
ECUs B, C and D are 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.

AC204742BM

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

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

TROUBLESHOOTING

CONTROLLER AREA NETWORK (CAN)

54C-15

TROUBLESHOOTING

CAN BUS DIAGNOSTICS TABLE

M1548300202589

CAUTION

• A diagnosis code may not also be set in the

CAN-B lines under the conditions below. If no
diagnosis code has been set due to electrical
noise, confirm diagnosis item 25 .

• Open circuit at the CAN_H side of the

CAN-B bus lines

• Open circuit at the CAN_L side of the CAN-

B bus line

• Short to earth at the CAN_H side of the

CAN-B bus line

• During diagnosis, a diagnosis code associ-

ated with another system may be set when
the ignition switch is turned on with connec-
tor(s) disconnected. After completing the

repair, confirm all systems for diagnosis
code(s). If diagnosis code(s) are set, erase
them all.

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

Time-out
diagnosis 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 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.

AC204742 BR

DATA LINK

CONNECTOR

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

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

Trouble in
CAN bus line
(b)

It must be assumed that a fault
was present in CAN bus line (b)
when the ETACS-ECU has set a
time-out diagnosis code for ECU
A, B, C and D.

AC204742BP

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

ETACS-ECU
(Gateway)

Diagnosis
connector

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

Diagnosis
code to be set

Possible
trouble spot

Logic for narrowing down trouble spot