Mitsubishi Grandis. Manual - part 993

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-24

YES : 

Return to Step 1.

NO : 

The procedure is complete.

Code No.B1401: Driver's Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit)
Code No.B1481: Driver's Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit)

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

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

CLOCK 
SPRING

SRS-ECU

: CONNECTOR LOCK SWITCH
  CONNECTOR CONNECTED: ON
  CONNECTOR DISCONNECTED: OFF

NOTE

CONNECTOR
LOCK SWITCH

Driver's Air Bag Module (1st and 2nd Squib) Circuit

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-25

CAUTION

If diagnosis code B1401 <1st squib> or B1481 
<2nd squib> 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 analog 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 SRS 
air bag will inflate. 

• The ignition signal is input to the air bag module 

via the clock spring to inflate the air bag.

DIAGNOSIS CODE SET CONDITIONS

• This diagnosis code is set if there is abnormal 

resistance between the input terminals of the 
driver's side air bag module (squib). The most 
likely causes for this code to be set are the 
followings: 

• Open circuit in the driver's air bag module 

(squib) or harness

• Open circuit in the clock spring

• Malfunction of connector contact

However, if no diagnosis code reset, the SRS 
warning lamp will be switched off (diagnosis code will 
be retained). 

PROBABLE CAUSES

• Open circuit in the clock spring

• Open circuit due to improper neutral position of 

the clock spring

• Open circuit in the driver's air bag module (squib) 

circuit

• Disengaged driver's air bag module (squib) 

connector

• Improper connector contact

• Malfunction of the SRS-ECU

DIAGNOSIS

STEP 1. MUT-III diagnosis code

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

).

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

(2) Slide the outer housing of the driver’ s air bag 

module connector C-303 in the arrow direction 
shown, and disconnect the connector.

(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 MB991866 into clock spring 

side of driver’s air bag module connector C-303 
(terminal No.1 and 2 <1st squib> or terminal No.3 
and 4 <2nd squib>) by backprobing.

AC306561AH

Outer housing of the 
driver's air bag module connector C-303

AC306758AD

C-303 Air bag
module
connector

MB991865
(Dummy resistor : 3

ΩΩ

MB991866
(Resistor harness)

(rear view

Ω

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-26

(5) Connect the negative battery terminal.

CAUTION

Always diagnosis code B1481 is set when 
checking diagnosis code B1401. This is because 
the second side terminal is isolated when 
checking it, diagnosis code B1481 is set but this 
is not a fault. In addition, always diagnosis code 
B1401 is set when checking diagnosis code 
B1481 because the first side terminal is isolated. 
(6) Erase the diagnosis code memory, and check the 

diagnosis code.

Q: Is the checked diagnosis code set?

YES : 

Go to Step 4.

NO : 

Replace the driver's air bag module. (Refer 
to 

P.52B-225

). Then go to Step 6.

STEP 4. Check the clock spring. (MUT-III 
diagnosis code.)
(1) Disconnect the negative battery terminal.

(2) Disconnect the clock spring connector C-309.

(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 MB991866 into harness side of 

clock spring connector C-309 (terminal No.4 and 
3 <1st squib> or terminal No.1 and 2 <2nd 
squib>) by backprobing.

(5) Connect the negative battery terminal.

CAUTION

Always diagnosis code B1481 is set when 
checking diagnosis code B1401. This is because 
the second side terminal is isolated when 
checking it, diagnosis code B1481 is set but this 
is not a fault. In addition, always diagnosis code 
B1401 is set when checking diagnosis code 
B1481 because the first side terminal is isolated. 
(6) Erase the diagnosis code memory, and check the 

diagnosis code.

Q: Is the checked diagnosis code set?

YES : 

Go to Step 5.

NO : 

Replace the clock spring. (Refer to 

P.52B-225

). Then go to Step 6.

AC310153AH

Connectors: C-309 <LHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

AC310183

AH

Connector: C-309 <RHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

AC306767

AC306767

C-309 Clock spring
connector

AC

(rear view)

MB991865
(Dummy resistor : 3

ΩΩ

MB991866
(Resistor harness)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-27

STEP 5. Check the harness between the 
SRS-ECU connector C-119 (terminal No.36 and 37 
<1st squib> or terminal No. 33 and 34 <2nd 
squib>) and the clock spring connector C-309 
(terminal No.3 and 4 <1st squib> or terminal No.1 
and 2 <2nd squib>) for open circuit.

(1) Disconnect SRS-ECU connector C-119 and clock 

spring connector C-309.

CAUTION

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

terminals.
<1st squib>

• SRS-ECU connector C-119 (terminal No.36) 

and the clock spring connector C-309 
(terminal No.3)

• SRS-ECU connector C-119 (terminal No.37) 

and the clock spring connector C-309 
(terminal No.4)

<2nd squib>

• SRS-ECU connector C-119 (terminal No.33) 

and the clock spring connector C-309 
(terminal No.1)

• SRS-ECU connector C-119 (terminal No.34) 

and the clock spring connector C-309 
(terminal No.2)

OK: Less than 2 

Ω

Q: Are the check results normal? 

YES : 

Erase the diagnosis code memory, and 

check the diagnosis code. If diagnosis code 
B1401 <1st squib> or B1481 <2nd squib> 
set, replace the SRS-ECU. (Refer to 

P.52B-223

). Then go to Step 6. 

NO : 

Replace the harness wires between 
SRS-ECU connector C-119 and clock spring 
connector C-309. Then go to Step 6.

AC311438 AD

C-119 (Y)

Connector: C-119

Harness side
(front view)

AC310153AH

Connectors: C-309 <LHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

AC310183

AH

Connector: C-309 <RHD>

Clock
spring

C-309 (Y)

Harness side
(rear view)

1

4

3

2

AC313270

42

31

38

27

21

41

28

39

22

30

25

47

36

33

44

34

45

37

48

26

29

23

40

32

43

35

46

24

B

A

C-309
Harness side
connector
(rear view)

C-119 Harness
side connector
(rear view)

AB

<1st squib>

1

4

3

2

AC313271

42

31

38

27

21

41

28

39

22

30

25

47

36

33

44

34

45

37

48

26

29

23

40

32

43

35

46

24

B

A

C-309
Harness side
connector
(rear view)

C-119 Harness
side connector
(rear view)

AB

<2nd squib>