Mitsubishi 380. Manual — part 790

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-84

STEP 3. Check the front impact sensor (LH) power supply
circuit. Measure the voltage at the front impact sensor (LH)
connector A-23.
(1) Disconnect the negative battery terminal.
(2) Disconnect front impact sensor (LH) connector A-23, 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 A-23 harness side connector

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

Q: Is the measured voltage within the specified range?

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

P.52B-231

). Then go to Step 5.

NO : Go to Step 4.

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 B1417 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.

AC305210

CONNECTOR: A-23

AT

A-23 (Y)

HARNESS SIDE

AC308161

A-23 HARNESS SIDE
CONNECTOR
(REAR VIEW)

AC

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)

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-85

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 B1417 set?

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

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-86

DTC B1418: Front Impact Sensor (LH) (Squib) for Power Supply Circuit
DTC B1419: Front Impact Sensor (LH) (Squib) for Communication System

CAUTION

If DTC B1418 or B1419 is set in the SRS-ECU,
always diagnose the CAN main bus line.

.

CIRCUIT OPERATION

The front 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 front air
bags should be deployed, it sends a fire signal to the
SRS-ECU to deploy the front air bags. In addition,
the CPU diagnoses the internal components of the
front 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
front impact sensor (LH) and the SRS-ECU is not
possible or faulty.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Malfunction of the front impact sensor (LH)

• Malfunction of the SRS-ECU

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

.

DIAGNOSIS

Required Special Tool:

• 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)

• MB991223 (MB991222): Harness set (Probe)

AC305210

CONNECTOR: A-23

AW

A-23 (Y)

52DB010A

CONNECTOR: C-11

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)

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-87

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 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 ).

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827