Mitsubishi Grandis. Manual - part 1017

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-120

Code No.B1452: Curtain air bag module (squib) (LH) system (short-circuited to the earth)

CAUTION

If diagnosis code B1452 is set in the SRS-ECU, 
always diagnose the CAN main bus line.

OPERATION

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

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if the curtain air bag 
module squib (LH) wire(s) are short-circuited to the 
earth.

PROBABLE CAUSES

• Damaged wiring harnesses or connectors

• Short to the earth in the curtain air bag module 

(squib) (LH) harness

• Malfunction of the SRS-ECU

DIAGNOSTIC PROCEDURE

STEP 1. MUT-III CAN bus diagnostics

Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

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

P.54D-16

).

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

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

: CONNECTOR
  CONNECTED: ON
  CONNECTOR
  DISCONNECTED: OFF

NOTE

CURTAIN AIR BAG
MODULE
(SQUIB) (LH)

Curtain Air Bag Module (Squib) (LH) Circuit

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-121

STEP 2. Check whether the diagnosis code is 
reset.

Check again if the diagnosis code is set.
(1) Erase the diagnosis code.
(2) Ignition: LOCK (OFF) position to ON
(3) On completion, check that the diagnosis code is 

not reset.

Q: Is the diagnosis code set?

YES : 

Go to Step 3.

NO : 

There is an intermittent malfunction such as 
poor engaged connector(s) or open circuit 
(Refer to GROUP 00, How to Cope with 
Intermittent Malfunction 

P.00-5

).

STEP 3. Check the curtain air bag module (LH). 
(MUT-III diagnosis code.)
(1) Disconnect the negative battery terminal.

(2) Disconnect the intermediate connector G-22 

(connection between rear floor harness and floor 
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) Insert special tool resistor harness probe into 

floor harness side connector G-22 by 
backprobing.

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

diagnosis code.

Q: Is diagnosis code B1452 set?

YES : 

Go to Step 4.

NO : 

Go to Step 5.

STEP 4. Check the curtain air bag module (LH) 
circuit. Resistance measurement at the SRS-ECU 
connector C-120.

(1) Disconnect SRS-ECU connector C-120.

(2) Disconnect the intermediate connector G-22 

(connection between rear floor harness and floor 
harness).

CAUTION

Do not insert a test probe into the terminal from 
its front side directly as the connector contact 
pressure may be weakened.
(3) Resistance measurement between C-120 

harness side connector terminals 5, 6 and body 

AC302576AE

 G-22 (R)

Connector: G-22

Floor harness
side (front view)

Third seat
belt (LH)

Second seat
belt (LH)

2 1

AC006042CA

MB991866
(Resistor harness)

G-22 Floor harness
connector

G-22 Rear floor
harness connector

MB991865
(Dummy resistor : 3

ΩΩ

AC311438 AE

C-120 (Y)

Connector: C-120

Harness side
(front view)

AC302576AE

 G-22 (R)

Connector: G-22

Floor harness
side (front view)

Third seat
belt (LH)

Second seat
belt (LH)

2 1

AC301563

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AC

C-120
Harness side 
connector 
(rear view)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-122

earth.

OK: Open circuit

Q: Is the check result normal?

YES : 

Go to Step 6.

NO : 

Repair the harness wire between SRS-ECU 
connector C-120 (terminal No.5 and 6) and 
intermediate connector G-22 (floor harness 
side, terminal No.1 and 2).

STEP 5. Check the curtain air bag module (LH) 
circuit. Resistance measurement at the 
intermediate connector G-22.

(1) Disconnect the intermediate connector G-22 

(connection between rear floor harness and floor 
harness).

(2) Disconnect curtain air bag module (LH) 

connector G-01. Use a flat-tipped screwdriver to 
unlock the locking button at the harness side 
connector by withdrawing it toward you in two 
stages, and then disconnect the connector.

CAUTION

Do not insert a test probe into the terminal from 
its front side directly as the connector contact 
pressure may be weakened.
(3) Resistance measurement between G-22 rear 

floor harness side connector terminals 1, 2 and 
body earth.

OK: Open circuit

Q: Is the check result normal?

YES : 

Replace the curtain air bag module (LH) 

(Refer to 

P.52B-231

). 

NO : 

Repair the harness wire between 
intermediate connector G-22 (terminal No.1 
and 2) and curtain air bag module (LH) 
connector G-01 (terminal No.1 and 2).

STEP 6. Check whether the diagnosis code is 
reset.

Q: Is diagnosis code B1452 set?

YES : 

Replace the SRS-ECU (Refer to 

P.52B-223

). 

NO : 

An intermittent malfunction is suspected 
(Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

P.00-5

). 

AC302576AE

 G-22 (R)

Connector: G-22

Floor harness
side (front view)

Third seat
belt (LH)

Second seat
belt (LH)

2 1

AC303223

AC 

 G-01 (B)

Connector: G-01

Harness side
(front view)

Roof centre duct

AC208384AN

G-01
Curtain air bag
module connector 

Flat-tip screw
driver

Locking button

G-01
Harness side
connector

AC303710

2

1

AC

G-22 Rear floor harness 
connector (rear view)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-123

Code No.B1453: Curtain air bag module (squib) (LH) system (short-circuited to the power supply)

CAUTION

If diagnosis code B1453 is set in the SRS-ECU, 
always diagnose the CAN main bus line.

OPERATION

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

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if the curtain air bag 
module squib (LH) wire(s) are short-circuited to the 
power supply.

PROBABLE CAUSES

• Damaged wiring harnesses or connectors

• Short to the power supply in the curtain air bag 

module (squib) (LH) harness

• Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. MUT-III CAN bus diagnostics

Use the MUT-III to diagnose the CAN bus lines.

Q: Is the check result normal?

YES : 

Go to Step 2.

NO : 

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

P.54D-16

).

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

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

: CONNECTOR
  CONNECTED: ON
  CONNECTOR
  DISCONNECTED: OFF

NOTE

CURTAIN AIR BAG
MODULE
(SQUIB) (LH)

Curtain Air Bag Module (Squib) (LH) Circuit