Mitsubishi Colt Ralliart. Manual — part 451

TROUBLESHOOTING

POWER STEERING

37-71

TROUBLE SYMPTOM CHART

M1372007600344

CAUTION

During diagnosis, a diagnosis code associated
with other system may be set when the ignition
switch is turned on with connector(s) discon-
nected. On completion, confirm all systems for
diagnosis code(s). If diagnosis code(s) are set,
erase them all.

Trouble symptom

Inspection
procedure

Reference pages or
actions

The M.U.T.-III cannot communicate with the electric power
steering system.

1 <CAN
communication
system check>

P.37-72

2 <ECU power
supply circuit
system check>

P.37-74

Although the electric power steering warning lamp
illuminates, the diagnosis code is not stored.

3

P.37-78

The steering has become heavy, but the electric power
steering warning lamp does not illuminate (This is normal,
because the electric power steering is limiting assist
operation).
NOTE: If the vehicle is driven under heavy load (e.g.
consecutively turning the steering to full lock or severe
cornering), the electric power steering motor drive circuit will
become hot. In this case, the electric power steering system
will limit assist operation by decreasing the motor current to
avoid damage. In this case, the steering will become heavy,
but the electric power steering warning lamp does not
illuminate. If the circuit temperature reduces after a while,
the assist operation will return to the normal level.

−

Reproduce the steering
operation, which your
customer did. Check the
M.U.T.-III data list item
No.07 (assist limit
current), and confirm that
the electric power steering
system limited the assist
operation (Refer to

P.37-84

). Note that this is

not a failure.

When the ignition switch is turned on, the system does not
perform the bulb check for the electric power steering
warning lamp (The electric power steering warning lamp
does not illuminate until the engine is started).
NOTE: The ignition switch is turned to the ON position
(within approximately 0.3 second) again immediately after it
is turned to the LOCK (OFF) position, the electric power
steering warning lamp does not illuminate.

−

Replace the meter
assembly (Refer to
GROUP 54A,
Combination Meter

P.54A-68

).

Main

Index

Group

TOC

TROUBLESHOOTING

POWER STEERING

37-72

SYMPTOM PROCEDURES

Inspection Procedure 1: M.U.T.-III cannot communicate with electric power steering system <CAN
communication system check>.

ENGINE-CVT-ECU

DIAGNOSIS
CONNECTOR

FRONT SIDE

COMBINATION
METER

ABS-ECU

EPS-ECU

Wire colour code
B : Black
LG : Light green
G : Green
L: Blue
W : White
Y: Yellow
SB : Sky blue
BR : Brown
O : Orange
GR : Grey
R : Red
P : Pink
V : Violet
PU: Purple

CAN Communication Circuit

Main

Index

Group

TOC

TROUBLESHOOTING

POWER STEERING

37-73

COMMENTS ON TROUBLE SYMPTOM

If the M.U.T.-III cannot communicate with the electric
power steering system, the CAN bus lines may be
defective. If the electric power steering system does
not operate (power assist is not available), the elec-
tric power steering-ECU or its power supply may be
defective.

PROBABLE CAUSES

• Defective harness wire(s) or connector(s)

• Malfunction of the electric power steering-ECU

DIAGNOSIS PROCEDURE

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

AC206895

AC

Diagnosis

connector

MB991827

MB991824

MB991910

CAUTION

Before connecting or disconnecting the
M.U.T.-III, turn the ignition switch to the "LOCK"
(OFF) position.
(1) Connect M.U.T.-III to the 16-pin diagnosis

connector.

(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF)

position.

Q: Is the check result normal?

YES :

Check the ECU power supply circuit system

(Refer to

P.37-78

).

NO :

Repair the CAN bus line (Refer to GROUP
54D, Diagnosis

P.54D-13

).

Main

Index

Group

TOC

TROUBLESHOOTING

POWER STEERING

37-74

Inspection Procedure 2: M.U.T.-III cannot communicate with electric power steering system <ECU
power supply circuit system check>.

Power Supply and Earth Circuit

FUSIBLE
LINK

IGNITION
SWITCH (IG1)

4

ABS

ELECTRIC POWER
STEERING-ECU

Wire colour code
B : Black LG : Light green G : Green L : Blue W : White Y : Yellow SB : Sky blue
BR : Brown O : Orange GR : Grey R : Red P : Pink V : Violet PU : Purple

COMMENTS ON TROUBLE SYMPTOM

If the M.U.T.-III cannot communicate with the electric
power steering system, the CAN bus lines may be
defective. If the electric power steering system does
not operate (power assist is not available), the elec-
tric power steering-ECU or its power supply may be
defective.

PROBABLE CAUSES

• Defective harness wire(s) or connector(s)

• Malfunction of the electric power steering-ECU

Main

Index

Group

TOC