Mitsubishi Lancer (4A9 engine). Manual — part 246

SERVICE PRECAUTIONS

CONTROLLER AREA NETWORK (CAN)

54C-8

SERVICE PRECAUTIONS

M1548302100333

Warnings in diagnosis section

Details regarding warning

When servicing an CAN bus line, earth yourself
by touching a metal object such as an unpainted
water pipe. If you fail to do, a component
connected to the CAN bus line may be broken.

−

A digital multimeter should be used.

When measuring resistance value or voltage in
CAN bus lines, use a digital multimeter. If not
using a digital multimeter, the equipments, which
are connected through the CAN communication
lines, may be damaged.

When measuring the resistance, disconnect the
negative battery terminal.

Disconnect the negative battery terminal when
measuring the resistance value in the CAN bus
line. If you fail to do so, the equipments, which
are connected through the CAN communication
lines, may be damaged.

The test wiring harness should be used.

Always use the test harness when measuring the
voltage or resistance value at the female
connector. If you fail to do so, connectors may be
damaged.

The strand end of the twist wire should be within
10 cm from the connector.

AC203824

Within 10 cm

Connector

Twisted wire

AH

If you repair the wire due to a defective
connector or its terminal or harness wire, you
should cut the wire so that the strand end of the
twist wire should be within 10 cm from the
connector as shown. If it exceeds 10 cm, twist
the wiring harness just like the original twisted
wire. If the strand end exceeds 10 cm, a
communication error may be caused.

Strictly observe the specified wiring harness
repair procedure.

When you repair a CAN bus line, observe the
precautions on how to repair the CAN bus line
strictly. Refer to . If a new wire is added or a
splice point is modified for the CAN_L or CAN_H
line, an error in the CAN communication may be
caused.

CAUTION

CAUTION

CAUTION

CAUTION

CAUTION

CAUTION

PRECAUTIONS ON HOW TO REPAIR THE CAN BUS LINES

CONTROLLER AREA NETWORK (CAN)

54C-9

PRECAUTIONS ON HOW TO REPAIR THE CAN BUS LINES

M1548301900358

PRECAUTIONS ON HOW TO REPAIR THE CAN
BUS LINES

AC204696

Added wire

No good

4AB

• If the CAN bus line(s) are repaired, renew all the

twisted wires between the end connectors. If the
wiring harness is partially repaired, or only
CAN_L or CAN_H line is repaired, noise suppres-
sion is deteriorated, causing a communication
error.

AC203824

Within 10 cm

Connector

Twisted wire

AH

•

AC202856

ECU

ECU

ECU

ECU

Good

No good

Terminator resistor

Open
circuit
point

Open
circuit
point

Terminator resistor

AF

: Shows main bus line.
: Shows sub bus line.
: Shows restored CAN bus line.

If the connector or wire on the main bus line or
the sub-bus wire is replaced, the frayed end of
the twisted wire should be within 10 cm from the
connector. If it exceeds 10 cm, twist the wiring
harness just like the original twisted wire. If the
frayed end exceeds 10 cm, noise suppression is
deteriorated, causing a communication error.

• If a sub-bus line is repaired, splice a new wire

directly into the main bus line. If a new wire is
spliced into the sub-bus line, which is connected
to another device, the CAN communication will
be disabled.

PRECAUTIONS ON HOW TO REPAIR THE
TERMINATOR RESISTOR
If one-side terminator resistor is broken, the CAN
communication will continue although noise suppres-
sion is deteriorated. No diagnosis codes may be set
even if the terminator resistor was broken. If a dam-
age is found, replace the ECU which incorporates
the defective terminator resistor.

CAN BUS LINE REPAIR HARNESS (PART NAME
AND NUMBER)

Part name

Part number

Twist pair cable

MN151514

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

DIAGNOSTICS

M1548300100564

The M.U.T.-III CAN bus diagnostics carries out the
three checks below automatically, and then displays
current condition of the CAN bus lines according to

the check results.

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

CONTROLLER AREA NETWORK (CAN)

54C-10

CAN BUS LINE DIAGNOSTIC FLOW

AC507612

YES

NG

NO

AL

From other diagnosis

1. M.U.T.-III CAN bus
diagnostics

Go to ordinary diagnosis

OK for (2)
P code, B code,
C code or
U code (current trouble)

OK for (2)
U code (past trouble)

2. Pinpoint possible trouble spot
according to diagnosis code

· Open circuit in can bus line
· Broken terminator resistor
· Power supply to ECU poorly earthed

(2) Checking the communication condition of ECUs.

(1) Check if a transmission error (bus off) occurred in the
ETACS-ECU.

·

Short in CAN bus line to power

supply or earth.

·

Short between CAN bus lines.

1. M.U.T.-III CAN bus diagnostics

The M.U.T.-III diagnoses CAN bus lines in
accordance with the following strategy.
NOTE: After you determine whether the CAN-C
lines are in good condition, then determine
whether the CAN-B lines are in good condition.
Then confirm each judgement result on the
M.U.T.-III screen.

(1) Check that the ETACS-ECU sets a diagnosis

code.
You can narrow down the points to be
diagnosed by confirming an ETACS-ECU
diagnosis code.

(2) Checking the communication condition of

ECUs
The M.U.T.-III narrows down troubles in circuit
by itself. Its strategies are as follows.

AC204741

ECU B

ECU C

ECU D

ECU A

(a)

(b)

(c)

(h)

(d)

(e)

(f)

(g)

AD

ETACS-ECU
(Gateway)

Reference circuit

Diagnosis
connector

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

CONTROLLER AREA NETWORK (CAN)

54C-11