Mitsubishi Colt Ralliart. Manual - part 548

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-30

STEP 4. Check whether the diagnosis code is 
reset.

Q: Is diagnosis code 3F set?

YES : 

Replace the SRS-ECU (Refer to 

P.52B-143

). 

NO : 

An intermittent malfunction is suspected 
(Refer to GROUP 00, How to Cope with 
Intermittent Malfunction 

P.00-13

).

Code No.4A: Curtain air bag module (squib) (LH) system (short-circuited between terminals of the 
squib circuit) 

OPERATION

The SRS-ECU judges how severe a collision is by 
detecting signals from the side impact sensors and 
the side-airbag safing G-sensor. If the impact is over 
a predetermined level, the SRS-ECU sends an igni-
tion signal. At this time, if the side-airbag safing 
G-sensor is on, the curtain air bag module will 
deploy. 

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if one curtain air bag mod-
ule squib (LH) wire shorted to the other. However, if 
no diagnosis code resets, the SRS warning lamp will 
be switched off (diagnosis code will be retained).

PROBABLE CAUSES

• Improper engaged connector or defective short 

spring*

• Short circuit between the curtain air bag module 

(squib) (LH) circuit terminals

AC510222

CURTAIN AIR BAG
MODULE (SQUIB)
(LH)

AIR BAG
DRIVE CIRCUIT

SRS-ECU

MICRO COMPUTER

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   

CONNECTOR
LOCK
SWITCH

CONNECTOR
LOCK
SWITCH

NOTE

CONNECTOR
COUPLED: ON
CONNECTOR
UNCOUPLED: OFF

Curtain Air Bag Module (Squib) (LH) Circuit

AB

Main

Index

Group

TOC

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-31

• Damaged connector(s)

• Malfunction of the SRS-ECU

NOTE: *: The squib circuit connectors integrate a 
"short" spring (which prevents the air bag from 
deploying unintentionally due to static electricity by 
shorting the positive wire to the earth wire in the 
squib circuit when the connectors are disconnected). 
Therefore, if connector B-34, C-10 or C-13 is dam-
aged or improperly engaged, the short spring may 
not be released when the connector is connected.

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Q: Is diagnosis code 34 set?

YES : 

Go to Step 2.

NO : 

Go to Step 3.

STEP 2. Connector lock check: SRS-ECU 
connector B-34 (M.U.T.-III diagnosis code).
(1) Disconnect the negative battery terminal.

(2) Disconnect connectors B-34, and then reconnect 

them.

(3) Connector the negative battery terminal.
(4) Erase the diagnosis code memory, and check the 

diagnosis code.

Q: Is diagnosis code 4A set?

YES : 

Go to Step 3.

NO : 

The procedure is complete. It is assumed 
that diagnosis code 4A set as connector 
B-34 was engaged improperly.

STEP 3. Connector lock check: SRS-ECU 
connector B-34, intermediate connector C-13 and 
curtain air bag module connector C-10 (M.U.T.-III 
diagnosis code). 
(1) Disconnect the negative battery terminal.

(2) Disconnect connectors B-34, C-13 and C-10, and 

then reconnect them. For connector C-10, use a 
flat-tipped screwdriver to pull out the locking 
button at the harness side connector, and then 
disconnect the connector.

(3) Connector the negative battery terminal.

AC206285

AG

B-34 (Y)

Connector: B-34

Harness side 
connector 
(rear view)

343536373839404142

252627282930313233

2122

2324

AC206285

AG

B-34 (Y)

Connector: B-34

Harness side 
connector 
(rear view)

343536373839404142

252627282930313233

2122

2324

AC401577

Connector: C-10

C-10 (B)

Harness side
connector
(front view)

AC

AC208384BK

C-10
Curtain air bag
module connector 

Flat-tipped 
screwdriver

Locking button

C-10
Harness side
connector

AC209027

Connector: C-13 

C-13 (R)

Quarter panel

AC

Harness side

Main

Index

Group

TOC

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-32

(4) Erase the diagnosis code memory, and check the 

diagnosis code.

Q: Is diagnosis code 4A set?

YES : 

Go to Step 4.

NO : 

The procedure is complete. It is assumed 
that diagnosis code 4A set as connector 
B-34, C-13 or C-10 was engaged 
improperly.

STEP 4. Check the diagnosis code by connecting 
a dummy resistor (M.U.T.-III diagnosis code).
(1) Disconnect the negative battery terminal.

(2) Disconnect intermediate connector C-10 

(connection between curtain air bag wring 
harness and instrument panel wring harness). 

(3) Connect special tool dummy resistor (MB991865) 

to special tool resistor harness (MB991866).

CAUTION

Do not insert a test probe into the terminal from 
its front side directly as the connector contact 
pressure may be weakened.
(4) Connect special tool (MB991884) to the C-13 

harness side connector by back probing.

(5) Connect the negative battery terminal.
(6) Erase diagnosis code memory, and then check 

the diagnosis code.

Q: Is diagnosis code 4A set?

YES : 

Go to Step 5.

NO : 

Go to Step 6.

STEP 5. Resistance measurement at the 
SRS-ECU connector B-34.
(1) Disconnect the negative battery terminal.

(2) Disconnect SRS-ECU connector B-34.

DANGER

To prevents the air bag from deploying unin-
tentionally, disconnect the curtain air bag 
harness connector C-13 to short the squib 
circuit.

CAUTION

Insert an insulator such as a cable tie to a depth 
of 4mm or more, otherwise the short spring will 
not be released.
(3) Insert a cable tie [3 mm wide, 0.5 mm thick] 

between terminals 27, 28 and the short spring to 
release the short spring.

AC401577

Connector: C-10

C-10 (B)

Harness side
connector
(front view)

AC

AC006042 CK

MB991866
(Resistor harness)

C-13 

Intermediate h

arness side

connector

MB991865 (Dummy
resistor: 3

 

Ω)

C-13 Curtain air bag
module (LH) side connector

AC206285

AG

B-34 (Y)

Connector: B-34

Harness side 
connector 
(rear view)

343536373839404142

252627282930313233

2122

2324

AC209027

Connector: C-13 

C-13 (R)

Quarter panel

AC

Harness side

AC208764

Section
A - A

B-34
Harness side connector
(front view)

Cable tie

Short spring

4 mm or more

Terminal

AE

A

A

Main

Index

Group

TOC

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-33

CAUTION

Do not insert a test probe into the terminal from 
its front side directly as the connector contact 
pressure may be weakened.
(4) Resistance measurement between B-34 harness 

side connector terminals 27 and 28.

OK: Open circuit

Q: Is the check result normal?

YES : 

Go to Step 7.

NO : 

Repair the harness wire between SRS-ECU 
connector B-34 (terminal No.27 and 28) and 
harness side connector C-13 (terminal No.2 
and 1).

STEP 6. Resistance measurement at intermediate 
connector C-13.
(1) Disconnect the negative battery terminal.

DANGER

To prevents the air bag from deploying unin-
tentionally, disconnect the curtain air bag 
module connector C-10 to short the squib 
circuit.

(2) Disconnect curtain air bag module connector 

C-10. Use a flat-tipped screwdriver to pull out the 
locking button at the harness side connector, and 
then disconnect the connector.

(3) Disconnect intermediate connector C-13 

(connection between curtain air bag wiring 
harness and instrument panel wiring harness). 

CAUTION

Insert an insulator such as a cable tie to a depth 
of 4mm or more, otherwise the short spring will 
not be released.
(4) Insert a cable tie [3 mm wide, 0.5 mm thick] 

between terminals 1, 2 and the short spring to 
release the short spring.

CAUTION

Do not insert a test probe into the terminal from 
its front side directly as the connector contact 
pressure may be weakened.

AC100326

34 35 36 37 38 39 40 41 42

25 26 27 28 29 30 31 32 33

21 22

23 24

AS

B-34 Harness side 
connector 
(rear view)

AC401577

Connector: C-10

C-10 (B)

Harness side
connector
(front view)

AC

AC208384BK

C-10
Curtain air bag
module connector 

Flat-tipped 
screwdriver

Locking button

C-10
Harness side
connector

AC303537

4 mm or more

C-10 Curtain air bag 
module (LH) side 
connector 
(front view)

Terminal

Cable tie

A

Short
spring

Section
A - A

AK

A

1 2

AC303538AH

C-13 Curtain air bag module (LH) 
side connector (rear view)

Main

Index

Group

TOC