Mitsubishi 380. Manual - part 791

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-88

STEP 3. Check for any diagnostic trouble code. (Using 
diagnostic tool MB991958, read the diagnostic trouble 
code.)
Check the front impact sensor (LH).
(1) Disconnect the negative battery terminal.
(2) Replace the front impact sensor (LH) with the front impact 

sensor (RH).

(3) Connect the negative battery terminal.
(4) Erase diagnostic trouble code from memory, and check the 

diagnostic trouble code.

Q: Is DTC B1408 or B1409 set?

YES : Replace the front impact sensor (LH) with a new one 

(Refer to 

P.52B-247

). Then go to Step 5.

NO :  Go to Step 4.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-89

STEP 4. Check the harness wires for open circuit or short 
circuit between SRS-ECU connector C-121 (terminal No.48 
and 47) and front impact sensor (LH) connector A-23 
(terminal No.1 and 2).
Q: Are the harness wires between SRS-ECU connector 

C-121 (terminal No.48 and 47) and front impact sensor 
(LH) connector A-23 (terminal No.1 and 2) in good 
condition? 
YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1418 or B1419 
sets, replace the SRS-ECU (Refer to 

P.52B-234

). 

Then go to Step 5.

NO :  Replace the harness wires between SRS-ECU 

connector C-121 and front impact sensor (LH) 
connector A-23. Then go to Step 5.

STEP 5. 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 DTC B1418 or B1419 set?

YES : Return to Step 1.
NO :  The procedure is complete.

AC305210

CONNECTOR: A-23

AT

A-23 (Y)

HARNESS SIDE

24DB062A

CONNECTOR: C-121

C-121 (Y)

SRS-ECU

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-121

INSTRUMENT

HARNESS

CONNECTOR

(REAR VIEW)

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-90

DTC B1420: Side-Airbag Module (RH) (Squib) System Fault 1 (Short Circuit between Terminals of the 
Squib Circuit)

CAUTION

If DTC B1420 is set in the combination meter, 
always diagnose the CAN bus lines.

.

CIRCUIT 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 predeter-
mined level, the SRS-ECU sends an ignition sig-
nal. 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.

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the side-airbag mod-
ule (RH) (squib).

.

TROUBLESHOOTING HINTS

• Improper engaged connector or defective short 

spring*

• Short between the side-airbag module (RH) 

(squib) circuit terminals

• Damaged connector(s)

• Malfunction of the SRS-ECU

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

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 ground wire in the 
squib circuit when the connectors are disconnected) 
(Refer to 

P.52B-3

). Therefore, if connector D-26 or 

D-32 is damaged or improperly engaged, the short 
spring may not be released when the connector 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 (Vehicles with CAN 

communication system)

• MB991865: Dummy resister

• MB991866: Resistor harness

24DB063A

CONNECTOR: D-26

SRS-ECU

63

55

51

69

61

66

58

65

64

5657

68

60

67

59

70

62

53

52 B A

54

D-26  (Y)

D-26 FLOOR

HARNESS

CONNECTOR

(REAR VIEW)

AC307779

D-32 (R)

AC

CONNECTOR : D-32

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-91

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

Q: Is the check result satisfactory?

YES : Go to Step 2
NO :  Repair the CAN bus lines (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