Content .. 811 812 813 814 ..

Mitsubishi 380. Manual - part 813

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-176

DTC B1470: Seat Belt Pre-Tensioner (LH) (Squib) System Fault 1 (Short Circuit between Terminals of
the Squib Circuit)

CAUTION

If DTC B1470 is set in the SRS-ECU, always diag-
nose the CAN main bus line.

CIRCUIT 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 pre-tensioner will deploy.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance
between the input terminals of the passenger's side
seat belt pre-tensioner (squib).

TROUBLESHOOTING HITS

• Improper engaged connector or defective short

spring*

• Short circuit between the passenger's seat belt

pre-tensioner (squib) circuit terminals

• Damaged connector(s)

• Malfunction of the SRS-ECU

• Refer to circuit diagrams GROUP-

• Refer to configuration diagrams GROUP-

NOTE: *: The squib circuit connectors integrate a
"short" spring (which prevents the seat belt pre-ten-
sioner from deploying unintentionally due to static
electricity by shorting the positive wire to the ground
wire in the squib circuit when the connectors are dis-
connected) (Refer to

P.52B-3

). Therefore, if connec-

tor D-27 or D-21 is damaged or improperly engaged,
the short spring may not be released when the con-
nector is connected.

DIAGNOSIS

Required Special Tools:

• MB991958: diagnostic tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

• MB991865: Dummy resister

• MB991884: Resistor harness (For Pre-tensioner)

24DB064A

CONNECTOR: D-27

SRS-ECU

D-27 (Y)

1 2

3 4

D-27 Floor

harness

connector

(rear view)

AC306920AB

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-177

STEP 1. Using diagnostic tool MB991958, diagnose the
CAN bus line.

CAUTION

To prevent damage to diagnostic tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting diagnostic tool
MB991958.
(1) Connect diagnostic tool MB991958. Refer to "How to

connect the diagnostic tool

P.52B-19

(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES : Go to Step 2.
NO : Repair the CAN bus line (Refer to GROUP 54C,

Diagnosis ).

STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC 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 Use Troubleshooting/Inspection
Service Points

− How to Cope with Intermittent

Malfunctions ).

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-178

STEP 3. Using diagnostic tool MB991958, read the
diagnostic trouble code.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOOK (OFF)" position.

Q: Is DTC B1519 set?

YES : Go to Step 4.
NO : Go to Step 5.

STEP 4. Check the SRS-ECU connector D-27.
Q: Is the connector correctly engaged?

YES : Go to Step 5.
NO : Engage the connector correctly. Then go to Step 9.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

24DB064A

CONNECTOR: D-27

SRS-ECU

D-27 (Y)

1 2

3 4

D-27 Floor

harness

connector

(rear view)

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-179

STEP 5. Check SRS-ECU connector D-27 and passenger’s
seat belt pre-tensioner connector D-21. (Using diagnostic
tool MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect connectors D-27 and D-21, and then reconnect

them. For connector D-21, 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) Connector the negative battery terminal.
(4) Erase the diagnostic trouble code memory, and check the

diagnostic trouble code.

Q: Is DTC B1470 set?

YES : Go to Step 6.
NO : The procedure is complete. It is assumed that DTC

B1470 set because connector D-27 or D-21 was
engaged improperly.

STEP 6. Check the passenger's seat belt pre-tensioner.
(Using diagnostic tool MB991958, read the diagnostic
trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect passenger's seat belt pre-tensioner connector

D-21. 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 MB991865 to special tool MB991884.
(4) Connect special tool MB991884 to the D-21 harness side

connector.

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

diagnostic trouble code.

Q: Is DTC B1470 set?

YES : Go to Step 7.
NO : Replace the passenger's seat belt pre-tensioner

(Refer to

P.52B-250

). Then go to Step 9.

AC306920AC

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

HARNESS SIDE
CONNECTOR
(FRONT VIEW)

2 1

24DB064A

CONNECTOR: D-27

SRS-ECU

D-27 (Y)

1 2

3 4

D-27 Floor

harness

connector

(rear view)

AC306920AC

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

HARNESS SIDE
CONNECTOR
(FRONT VIEW)

2 1

MB991884

MB991885

AC103283AO

MB991865
(DUMMY RESISTOR : 3Ω)

MB991884
(RESISTOR
HARNESS)

D-21 HARNESS SIDE
CONNECTOR

Content .. 811 812 813 814 ..