Mitsubishi 380. Manual - part 806

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-148

DTC B1438: Side Impact Sensor (LH) (Squib) for Power Supply Circuit
DTC B1439: Side Impact Sensor (LH) (Squib) for Communication System

CAUTION

If DTC B1438 or B1439 is set in the SRS-ECU, 
always diagnose the CAN main bus line.

.

CIRCUIT OPERATION

The side impact sensor includes an analog G sensor 
and CPU, etc. The CPU monitors the analog G sen-
sor output signal. If the CPU judges that the side-air-
bags should be deployed, it sends a fire signal to the 
SRS-ECU to deploy the side-airbags. In addition, the 
CPU diagnoses the internal components of the side 
impact sensor. If a malfunction occurs, it requests the 
SRS-ECU to set a diagnostic trouble code.

.

DTC SET CONDITIONS

These DTCs are set if communication between the 
side impact sensor (LH) and the SRS-ECU is not 
possible or faulty.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Malfunction of the side impact sensor (LH)

• 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)

AC305250

CONNECTOR: D-20

AI

FRONT SEAT BELT

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-149

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)

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-150

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 for any diagnostic trouble code. (Using 
diagnostic tool MB991958, read the diagnostic trouble 
code.)
Check the side impact sensor (LH).
(1) Disconnect the negative battery terminal.
(2) Replace the side impact sensor (LH) with the side 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 B1428 or B1429 set?

YES : Replace the side 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

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-151

STEP 4. Check the harness wires for open circuit or short 
circuit between SRS-ECU connector D-27 (terminal No.19 
and 20) and side impact sensor (LH) connector D-20 
(terminal No.1 and 2).
Q: Are the harness wires between SRS-ECU connector 

D-27 (terminal No.19 and 20) and side impact sensor 
(LH) connector D-20 (terminal No.1 and 2) in good 
condition? 
YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1438 or B1439 
sets, replace the SRS-ECU (Refer to 

P.52B-234

). 

Then go to Step 5.

NO :  Replace the harness wires between SRS-ECU 

connector D-27 and side impact sensor (LH) 
connector D-20. 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 B1438 or B1439 set?

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

AC305250

CONNECTOR: D-20

AJ

FRONT SEAT BELT

HARNESS SIDE
CONNECTOR
(REAR VIEW)

2

1

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)

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827