Mitsubishi 380. Manual — part 805

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-144

DTC B1437: Side Impact Sensor (LH) Power Supply Circuit System

CAUTION

If DTC B1437 is set in the SRS-ECU, always diag-
nose 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

This DTC is set if the power supply voltage of the
side impact sensor (LH) drops below the rated value
for a continuous period of 5 seconds or more. How-
ever, DTC B1437 will be automatically cleared and
the SRS warning light will switch off if the condition
returns to normal.

.

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-145

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

• 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-146

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 side impact sensor (LH) power supply
circuit. Measure the voltage at the side impact sensor (LH)
connector D-20.
(1) Disconnect the negative battery terminal.
(2) Disconnect side impact sensor (LH) connector D-20, and

measure at the wiring harness side.

(3) Connect the negative battery terminal.
(4) Turn the ignition switch to the "ON" position.

CAUTION

Do not insert a test probe into the terminal from its front
side directly, as the connector contact pressure may be
weakened.
(5) Measure the voltage between the D-20 harness side

connector terminal 2 and body ground.
Voltage should measure 9 volts or more.

Q: Is the measured voltage within the specified range?

YES : Replace the side impact sensor (LH) (Refer to

P.52B-247

). Then go to Step 5.

NO : Go to Step 4.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305250

CONNECTOR: D-20

AJ

FRONT SEAT BELT

HARNESS SIDE
CONNECTOR
(REAR VIEW)

2

1

AC201627

1 2

D-20 HARNESS SIDE
CONNECTOR
(REAR VIEW)

AU

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-147

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 B1437 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 B1437 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