Mitsubishi 380. Manual — part 777
SRS AIR BAG DIAGNOSIS
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-32
DTC B1401: Driver's Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit)
CAUTION
If DTC B1401 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 SRS
air bag will inflate.
• The ignition signal is input to the air bag module
via the clock spring to inflate the air bag.
.
DTC SET CONDITIONS
• This DTC is set if there is abnormal resistance
between the input terminals of the driver's side air
bag module (squib). The most likely causes for
this code to be set are the followings:
• Open circuit in the driver's air bag module
(squib) or harness
• Open circuit in the clock spring
• Malfunction of connector contact
However, if no DTC reset, the SRS warning light will
be switched off (DTC will be retained).
.
TROUBLESHOOTING HINTS
• Refer to circuit diagrams GROUP-
• Refer to configuration diagrams GROUP-
• Open circuit in the clock spring
• Open circuit due to improper neutral position of
the clock spring
• Open circuit in the driver's air bag module (squib)
circuit
• Disengaged driver's air bag module (squib) con-
nector
• Improper connector contact
• Malfunction of the SRS-ECU
.
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 resistor
• MB991866: Resistor harness
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)
52DB006A
C-307 (Y)
CONNECTORS: C-305, C-307
CLOCK
SPRING
C-305 (Y)
SRS AIR BAG DIAGNOSIS
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-33
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
."
(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
SRS AIR BAG DIAGNOSIS
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-34
STEP 3. Check the driver's air bag module. (Using
diagnostic tool MB991958, read the diagnostic trouble
code.)
(1) Disconnect the negative battery terminal.
(2) Slide the outer housing of the driver’ s air bag module
connector C-305 in the arrow direction shown, and
disconnect the connector.
(3) Connect special tool MB991865 to special tool MB991866.
CAUTION
Do not insert a test probe into the terminal from its front
side directly, as the connector contact pressure may be
weakened.
(4) Insert special tool MB991866 into clock spring side of
driver’s air bag module connector C-305 (terminal No.1 and
2 ) by testprobe.
(5) Connect the negative battery terminal.
(6) Erase the diagnostic trouble code memory, and check the
diagnostic trouble code.
Q: Is DTC B1401 set?
YES : Go to Step 4.
NO : Replace the driver's air bag module (Refer to
). Then go to Step 6.
AC306561AC
OUTER HOUSING OF THE DRIVER'S
AIR BAG MODULE CONNECTOR C-305
AC306758 AB
C-305 AIR BAG
MODULE
CONNECTOR
MB991865
(DUMMY RESISTOR : 3Ω)
MB991866 (RESISTOR
HARNESS)
(REAR VIEW)
SRS AIR BAG DIAGNOSIS
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-35
STEP 4. Check the clock spring. (Using diagnostic tool
MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect the clock spring connector C-307.
(3) Connect special tool MB991865 to special tool MB991866.
CAUTION
Do not insert a test probe into the terminal from its front
side directly, as the connector contact pressure may be
weakened.
(4) Insert special tool MB991866 into harness side of clock
spring connector C-307 (terminal No.14 and 13 ) by
testprobe.
(5) Connect the negative battery terminal.
(6) Erase the diagnostic trouble code memory, and check the
diagnostic trouble code.
Q: Is DTC B1401 set?
YES : Go to Step 5.
NO : Replace the clock spring (Refer to
). Then
go to Step 6.
52DB008A
C-307 (Y)
CONNECTOR: C-307
C-307 HARNESS
SIDE CONNECTOR
CLOCK
SPRING
11
12
13
14
AC306767
C-307 CLOCK SPRING
CONNECTOR
AB
MB991865
(DUMMY RESISTOR : 3Ω)
MB991866 (RESISTOR
HARNESS)
1112 14
13
(REAR VIEW)
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