Mitsubishi Grandis. Manual - part 1024

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-148

stages, and then disconnect the connector.

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 7, 8 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.
(4) Check for continuity between C-120 harness side 

connector terminals 7 and 8.

OK: Open circuit.

Q: Is the check result normal?

YES : 

Go to Step 8.

NO : 

Repair the harness wires between 
SRS-ECU connector C-120 (terminal No.7 
and 8) and seat belt pre-tensioner (LH) 
connector D-19 (terminal No.1 and 2).

STEP 8. Check whether the diagnosis code is 
reset.

Q: Is diagnosis code B1470 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

). 

AC308175AD

A

A

C-120 Harness side
connector (front view)

Terminal

Short spring

4 mm or more

Sec-
tion
A - A

Cable tie

AC308181

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AD

C-120 Harness side
connector (rear view)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-149

Code No.B1471: Seat Belt Pre-Tensioner (LH) (Squib) System Fault 2 (Open in the Squib Circuit)

CAUTION

If diagnosis code B1471 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 front impact sensors and 
the front air bag analogue G-sensor. If the impact is 
over a predetermined level, the SRS-ECU sends an 
ignition signal. At this time, if the front air bag safing 
G-sensor is on, the pre-tensioner will deploy. 

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if there is abnormal 
resistance between the input terminals of the seat 
belt pre-tensioner (LH) (squib).

PROBABLE CAUSES

• Improper connector contact

• Open circuit in the seat belt pre-tensioner (LH) 

(squib) circuit

• 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

).

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

).

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

SEAT BELT
PRETENSIONER
(LH)

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

: CONNECTOR
  CONNECTED: ON
  CONNECTOR
  DISCONNECTED: OFF

NOTE

Seat Belt Pre-Tensioner (LH) (Squib) Circuit

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-150

STEP 3. Check the seat belt pre-tensioner (LH). 
(MUT-III diagnosis code.)
(1) Disconnect the negative battery terminal.

(2) Disconnect seat belt pre-tensioner (LH) 

connector D-19. 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.

(3) Connect special tool dummy resistor (MB991865) 

to special tool resistor harness (MB991884).

(4) Connect special tool MB991884 to the D-19 

harness side connector.

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

the diagnosis code.

Q: Is diagnosis code B1471 set?

YES : 

Go to Step 4.

NO : 

Replace the seat belt pre-tensioner (LH) 
(Refer to 

P.52B-239

).

STEP 4. Resistance measurement between 
SRS-ECU connector C-120 (terminal No.7 and 8) 
and the seat belt pre-tensioner (LH) connector 
D-19 (terminal No.1 and 2).

(1) Disconnect SRS-ECU connector C-120 and seat 

belt pre-tensioner (LH) connector D-19, and 
measure at the wiring harness side. For 
connector D-19, use a flat-tipped screwdriver to 
unlock the locking button at the harness side 
connector by with drawing it toward you in two 

AC302393AC

 D-19 (B)

Connector: D-19

Centre
pillar

Front vehicle

Harness side
(front view)

AC103556 AY

Locking button

Flat-tip screw
driver

D-19 Harness
side connector

D-19 Seat belt
pre-tensioner (LH)
connector

MB991884
MB991885

AC103283AV

MB991865
(Dummy resistor : 3

Ω)

MB991884
(Resistor
harness)

D-19  Harness side
connector

AC311438 AE

C-120 (Y)

Connector: C-120

Harness side
(front view)

AC302393AC

 D-19 (B)

Connector: D-19

Centre
pillar

Front vehicle

Harness side
(front view)

AC103556 AY

Locking button

Flat-tip screw
driver

D-19 Harness
side connector

D-19 Seat belt
pre-tensioner (LH)
connector

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-151

stages, and then disconnect the connector.

(2) Connect D-19 harness side connector to special 

tool resistor harness (MB991884).

CAUTION

Do not insert a test probe into the terminal from 
its front side directly, as the connector contact 
pressure may be weakened.
(3) Check for continuity between the following 

terminals.

• SRS-ECU connector C-120 (terminal No.7) 

and the special tool (terminal No.2)

• SRS-ECU connector C-120 (terminal No.8) 

and the special tool (terminal No.1)

OK: Less than 2 

Ω

Q: Are the check results normal?

YES : 

Go to Step 5.

NO : 

Repair the harness wires between 
SRS-ECU connector C-120 (terminal No.7 
and 8) seat belt pre-tensioner (LH) 
connector D-19 (terminal No.1 and 2).

STEP 5. Check whether the diagnosis code is 
reset.

Q: Is diagnosis code B1471 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

). 

AC201287BH

D-19 
Harness side
connector

MB991884

AC308183

2

1

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AD

<D-19 Harness side
connector>
Special tool
MB991884
(front view)

C-120 Harness side
connector
(rear view)