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