Mitsubishi 380. Manual - part 817

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-192

DTC B1473: Seat Belt Pre-Tensioner (LH) (Squib) System Fault for Ground Circuit (Short-Circuited to 
Ground)

CAUTION

If DTC B1473 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 seat 
belt pre-tensioner (squib).

.

TROUBLESHOOTING HITS

• Damaged wiring harnesses or connectors

• Short to the ground in the passenger's seat belt 

pre-tensioner (squib) harness

• Malfunction of the SRS-ECU

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

.

24DB064A

CONNECTOR: D-27

SRS-ECU

D-27 (Y)

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

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-193

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 resistor

• MB991884: Resistor harness (For Pre-tensioner)

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 ).

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-194

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

STEP 3. 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 check the 

diagnostic trouble code.

Q: Is DTC B1473 set?

YES : Go to Step 4.
NO :  Replace the passenger's seat belt pre-tensioner. 

Refer to 

P.52B-250

. Then go to Step 6.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

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

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-195

STEP 4. Check the passenger's seat belt pre-tensioner 
circuit. Measure the resistance at the SRS-ECU connector 
D-27.
(1) Disconnect SRS-ECU connector D-27.

(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.

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 D-27 harness side connector 

terminals 7, 8 and body ground.
It should be open circuit.

Q: Does continuity exist?

YES : Go to Step 5.
NO :  Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1473 sets, 
replace the SRS-ECU (Refer to 

P.52B-234

). Then go 

to Step 6.

24DB064A

CONNECTOR: D-27

SRS-ECU

D-27 (Y)

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

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

24DB088A

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

D-27 FLOOR HARNESS 

SIDE CONNECTOR

(REAR VIEW)