Mitsubishi Grandis. Manual — part 1003

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-64

YES :

Go to Step 5.

NO :

Repair the harness wires between
SRS-ECU connector C-119 (terminal No.38
and 39) and front impact sensor (LH)
connector A-22 (terminal No.1 and 2).

STEP 5. Check whether the diagnosis code is
reset.

Q: Is diagnosis code B1418 or B1419 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

).

Code No.B1420: Side-Airbag Module (RH) (Squib) System Fault 1 (Short Circuit between Terminals of
the Squib Circuit)

CAUTION

If diagnosis code B1420 is set in the SRS-ECU,
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

• Improper engaged connector or defective short

spring*

• Short between the side-airbag module (RH)

(squib) circuit terminals

• Damaged connector(s)

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-65

• Malfunction of the SRS-ECU

NOTE: *: The squib circuit connectors integrate a
"short" spring (which prevents the air bag from
deploying unintentionally due to static electricity by
shorting the positive wire to the earth wire in the
squib circuit when the connectors are disconnected).
(Refer to

P.52B-5

). Therefore, if connector C-118 or

D-29 is damaged or improperly engaged, the short
spring may not be released when the connector is
connected.

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. MUT-III diagnosis code

CAUTION

To prevent damage to MUT-III MB991958, always
turn the ignition switch to the "LOCK" (OFF)
position before connecting or disconnecting
MUT-III MB991958.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the diagnosis code is set.
(3) Turn the ignition switch to the "LOOK (OFF)"

position.

Q: Is diagnosis code B1519 set?

YES :

Go to Step 4.

NO :

Go to Step 5.

STEP 4. Connector lock check: SRS-ECU
connector C-118 (MUT-III diagnosis code).
(1) Disconnect the negative battery terminal.

(2) Disconnect connectors C-118 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 B1420 out put?

YES :

Go to Step 5.

NO :

The procedure is complete. It is assumed
that diagnosis code B1420 set as connector
C-118 was engaged improperly.

STEP 5. Connector lock check: SRS-ECU
connector C-118 and side-airbag module (RH)
connector D-29 (MUT-III diagnosis code)
(1) Disconnect the negative battery terminal.

(2) Disconnect connectors C-118 and D-29, and then

reconnect them.

(3) Connect the negative battery terminal.

AC311438 AC

C-118 (Y)

Connector: C-118

Harness side
(front view)

AC311438 AC

C-118 (Y)

Connector: C-118

Harness side
(front view)

AC303522

AE

D-29 (R)

Connector: D-29

Harness side
(front view)

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-66

(4) Erase the diagnosis code memory, and check the

diagnosis code.

Q: Is diagnosis code B1420 out put?

YES :

Go to Step 6.

NO :

The procedure is complete. It is assumed
that diagnosis code B1420 set because
connector C-118 or D-29 was engaged
improperly.

STEP 6. 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 B1420 set?

YES :

Go to Step 7.

NO :

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

P.52A-24

).

STEP 7. 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 connector D-29.

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 57, 58 and the short spring to
release the short spring.

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)

AC301607AE

C-118 Harness side
connector (front view)

Terminal

Cable
tie

Section
A - A

4 mm or more

Short spring

A

A

TROUBLESHOOTING

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-67

(4) Measure at the wiring harness side.

CAUTION

Do not insert a test probe into the terminal from
its front side directly, as the connector contact
pressure may be weakened.
(5) Check for continuity between C-118 harness side

connector terminals 57 and 58.

OK: Open circuit

Q: Is the check result normal?

YES :

Go to Step 8.

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 8. Check whether the diagnosis code is
reset.

Q: Is diagnosis code B1420 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

).

Code No.B1421: Side-Airbag Module (RH) (Squib) System Fault 2 (Open in the Squib Circuit)

AC301573

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)

AF

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