Mitsubishi Grandis. Manual — part 1004

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-68

CAUTION

If diagnosis code B1421 is set in the combination
meter, always diagnose the CAN bus lines.

OPERATION

• The SRS-ECU judges how severe a collision is

by detecting signals from the left and right side
impact sensors. If the impact is over a
predetermined level, the SRS-ECU sends an
ignition signal. At this time, if the side-airbag
safing G-sensor is on, the SRS side-airbag will
inflate.

• The ignition signal is input to the side-airbag

module to inflate the side-airbag.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if there is abnormal
resistance between the input terminals of the
side-airbag module (RH) (squib).

PROBABLE CAUSES

• Open circuit in the side-airbag module (RH)

(squib) circuit

• Improper connector contact

• 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 lines (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 side-airbag module (RH).
(MUT-III diagnosis code.)
(1) Disconnect the negative battery terminal.

(2) Disconnect the side-airbag module (RH)

connector D-29.

(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 the D-29

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 B1421 set?

YES :

Go to Step 4.

NO :

Replace the seatback frame of the front
seat (RH). (Refer to GROUP 52A, Front
Seat

P.52A-24

).

AC303522

AE

D-29 (R)

Connector: D-29

Harness side
(front view)

AC006042BX

MB991866
(Resistor harness)

D-29 Harness side
connector

D-29 Side-airbag
module (RH) connector

MB991865 (Dummy
resistor: 3

Ω)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-69

STEP 4. Resistance measurement between
SRS-ECU connector C-118 (terminal No.57 and
58) and the side-airbag module (RH) connector
D-29 (terminal No.1 and 2).

(1) Disconnect SRS-ECU connector C-118 and

side-airbag module (RH) connector D-29.

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.

• SRS-ECU connector C-118 (terminal No.57)

and the side-airbag module (RH) connector
D-29 (terminal No.2)

• SRS-ECU connector C-118 (terminal No.58)

and the side-airbag module (RH) connector
D-29 (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-118 (terminal No.57
and 58) and side-airbag module (RH)
connector D-29 (terminal No.1 and 2).

STEP 5. Check whether the diagnosis code is
reset.

Q: Is diagnosis code B1421 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

).

AC311438 AC

C-118 (Y)

Connector: C-118

Harness side
(front view)

AC303522

AE

D-29 (R)

Connector: D-29

Harness side
(front view)

AC301580

1 2

63

55

51

69

61

66

58

65

64

56 57

68

60

67

59

70

62

53

52 B

A

54

C-118
Harness side
connector
(rear view)

D-29
Harness side
connector
(rear view)

AE

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-70

Code No.B1422: Side-Airbag Module (RH) (Squib) System Fault Earth Circuit (Short-Circuited to
Earth)

CAUTION

If diagnosis code B1422 is set in the combination
meter, always diagnose the CAN bus lines.

OPERATION

• The SRS-ECU judges how severe a collision is

by detecting signals from the left and right side
impact sensors. If the impact is over a
predetermined level, the SRS-ECU sends an
ignition signal. At this time, if the side-airbag
safing G-sensor is on, the SRS side-airbag will
inflate.

• The ignition signal is input to the side-airbag

module to inflate the side-airbag.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if there is abnormal
resistance between the input terminals of the
side-airbag module (RH) (squib).

PROBABLE CAUSES

• Damaged wiring harnesses or connectors

• Short to earth in the side-airbag module (RH)

(squib) 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 lines (Refer to GROUP
54D, Diagnosis-Can Bus Diagnostic Chart

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

SIDE AIR BAG
MODULE
(SQUIB) (RH)

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

: CONNECTOR
CONNECTED: ON
CONNECTOR
DISCONNECTED: OFF

NOTE

Side-Airbag Module (RH) (Squib) Circuit

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-71

STEP 3. Check the side-airbag module (RH).
(MUT-III diagnosis code.)
(1) Disconnect the negative battery terminal.

(2) Disconnect the side-airbag module (RH)

connector D-29.

(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 the D-29

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 B1422 set?

YES :

Go to Step 4.

NO :

Replace the seatback frame of the front
seat (RH). (Refer to GROUP 52A, Front
Seat

P.52A-24

).

STEP 4. Check the side-airbag module (RH)
circuit. Resistance measurement at the SRS-ECU
connector C-118.

(1) Disconnect SRS-ECU connector C-118.

DANGER

To prevent the air bag from deploying
unintentionally, disconnect the side-airbag
module (RH) connector D-29 to short the
squib circuit.

(2) Disconnect side-airbag module (RH) connector

D-29.

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 C-118 harness side

connector terminals 57, 58 and body earth.

OK: Open circuit

Q: Is the check result normal?

AC303522

AE

D-29 (R)

Connector: D-29

Harness side
(front view)

AC006042BX

MB991866
(Resistor harness)

D-29 Harness side
connector

D-29 Side-airbag
module (RH) connector

MB991865 (Dummy
resistor: 3

Ω)

AC311438 AC

C-118 (Y)

Connector: C-118

Harness side
(front view)

AC303522

AE

D-29 (R)

Connector: D-29

Harness side
(front view)

AC301576

63

55

51

69

61

66

58

65

64

56 57

68

60

67

59

70

62

53

52 B

A

54

C-118 Harness side
connector (rear view)

AE