Mitsubishi Lancer Evolution IX. Manual - part 628

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-25

STEP 2. Connector lock check: SRS-ECU 
connector C-12. (M.U.T.-II/III diagnosis code)
(1) Disconnect the negative battery terminal.

(2) Disconnect the connectors C-12 and then 

reconnect them.

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

diagnosis code.

Q: Is diagnosis code 24 set?

YES : 

Go to Step 4.

NO : 

The procedure is complete. It is assumed 
that diagnosis code 24 set as connector 
C-12 was engaged improperly.

STEP 3. Connector lock check: SRS-ECU 
connector C-12 and passenger’s (front) air bag 
module connector C-106. (M.U.T.-II/III diagnosis 
code)
(1) Disconnect the negative battery terminal.

(2) Disconnect connectors C-12 and C-106, and then 

reconnect them.

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

diagnosis code.

Q: Is diagnosis code 24 set?

YES : 

Go to Step 4.

NO : 

The procedure is complete. It is assumed 
that diagnosis code 24 set as connector 
C-12, or C-106 was engaged improperly.

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

(2) Disconnect passenger’s (front) air bag module 

connector C-106.

(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) Disconnect the passenger's (front) air bag 

module connector C-106 and insert special tool 
(MB991866) into the harness side connector by 
backprobing.

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

diagnosis code.

Q:  Is diagnosis code 24 set?

YES : 

Go to Step 5.

NO : 

Replace the passenger's (front) air bag 
module (Refer to 

P.52B-110

).

AC101950AJ

SRS-ECU

Harness side 
connector 
(rear view)
 

C-12 (Y)

Connector: C-12

AC101950AJ

SRS-ECU

Harness side 
connector 
(rear view)
 

C-12 (Y)

Connector: C-12

AC100985

Connector: C-106

Glove box striker

2

1

Harness side 
connector (rear view)

C-106 (R)

AQ

AC100985

Connector: C-106

Glove box striker

2

1

Harness side 
connector (rear view)

C-106 (R)

AQ

AC300956AL

MB991865
(Dummy resistor: 3    )

MB991866 

(Resistor harness)

C-106 Passenger's (front) 
air bag module connector

C-106 Harness side 

connector

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-26

STEP 5. Resistance measurement at SRS-ECU 
connector C-12.

(1) Disconnect SRS-ECU connector C-12.

(2) Disconnect passenger’s (front) air bag module 

connector C-106.

DANGER

To prevents the air bag from deploying unin-
tentionally, disconnect the passenger’s 
(front) air bag module connector C-106 to 
short the squib circuit.

(3) Disconnect the passenger's (front) air bag 

module connector C-106.

CAUTION

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

between terminals 9, 10 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.
(5) Resistance measurement between C-12 harness 

side connector terminals 9 and 10.

OK: Open circuit

Q: Is the check result normal? 

YES : 

Go to Step 6.

NO : 

Repair the harness wires between 
SRS-ECU connector C-12 (terminal No.9 
and 10) and passenger’s (front) air bag 
module connector C-106 (terminal No.2 and 
1).

STEP 6. Check whether the diagnosis code is 
reset.

Q: Is diagnosis code 24 set?

YES : 

Replace the SRS-ECU (Refer 

to

P.52B-109

).

NO : 

An intermittent malfunction is suspected 
(Refer to GROUP 00 

− How to Use 

Troubleshooting/Inspection Service Points 

P.00-5

). 

AC101950AJ

SRS-ECU

Harness side 
connector 
(rear view)
 

C-12 (Y)

Connector: C-12

AC100985

Connector: C-106

Glove box striker

2

1

Harness side 
connector (rear view)

C-106 (R)

AQ

AC006036

Section
A - A

C-12 
Harness side connector
(front view)

Cable tie

Short spring

4 mm or more

Terminal

AV

A

A

13 14 15 16 17 18 19 20

5 6 7 8 9 10 11 12

1 2

3 4

AC006044

C-12  
Harness side connector 
(rear view)

AQ

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-27

Code No.25: Passenger's (front) air bag module (squib) system (open-circuited in the squib circuit)

OPERATION

• The SRS-ECU judges how severe a collision is 

by detecting signals from the front impact sensors 
and the front air bag analogue G-sensor. If the 
impact is over a predetermined level, the 
SRS-ECU outputs an ignition signal. At this time, 
if the front air bag safing G-sensor is on, the SRS 
air bag will inflate. 

• The ignition signal is input to the air bag module 

to inflate the air bag.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if passenger’s (front) air 
bag squib wire(s) are open-circuited. However, if no 
diagnosis code resets, the SRS warning lamp will be 
switched off (diagnosis code will be retained). 

PROBABLE CAUSES

• Open circuit in the passenger's (front) air bag 

module (squib) circuit

• Improper connector contact

• Malfunction of the SRS-ECU

CONNECTOR
LOCK
SWITCH

CONNECTOR
LOCK
SWITCH

AIR BAG DRIVE
CIRCUIT

MICROCOMPUTER

SRS-ECU

AIR BAG MODULE
(SQUIB)
(PASSENGER'S SIDE)

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

Passenger's (Front) Air Bag Module (Squib) Circuit

NOTE

: CONNECTOR
  COUPLED: ON
  CONNECTOR
  UNCOUPLED: OFF

: LH drive  vehicles
: RH drive  vehicles

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-28

DIAGNOSIS PROCEDURE

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

(2) Disconnect passenger’s (front) air bag module 

connector C-106.

(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) Disconnect the passenger's (front) air bag 

module connector C-106, and insert special tool 
(MB991866) into the harness side connector by 
backprobing.

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

diagnosis code.

Q: Is diagnosis code 25 set?

YES : 

Go to Step 2.

NO : 

Replace the passenger's (front) air bag 
module (Refer to 

P.52B-110

).

STEP 2. Resistance measurement between 
SRS-ECU connector C-12 (terminal No9 and 10) 
and the passenger's (front) air bag module 
connector C-106 (terminal No.2 and 1)

(1) Disconnect passenger’s (front) air bag module 

connector C-106.

(2) Disconnect SRS-ECU connector C-12 and 

passenger's (front) air bag module connector 
C-106.

CAUTION

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

AC100985

Connector: C-106

Glove box striker

2

1

Harness side 
connector (rear view)

C-106 (R)

AQ

AC300956AL

MB991865
(Dummy resistor: 3    )

MB991866 

(Resistor harness)

C-106 Passenger's (front) 
air bag module connector

C-106 Harness side 

connector

AC100985

Connector: C-106

Glove box striker

2

1

Harness side 
connector (rear view)

C-106 (R)

AQ

AC101950AJ

SRS-ECU

Harness side 
connector 
(rear view)
 

C-12 (Y)

Connector: C-12

1 2

1 2

3 4

5 6 7 8 9 10 11 12

13 14 15 16

18 19 20

17

AC203891

C-12
Harness side 
connector 
(rear view)

C-106 Harness side connector 
(rear view)

AG