Mitsubishi Galant 9G. Manual — part 1478
SRS AIR BAG DIAGNOSIS
TSB Revision
SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-322
CAUTION
If DTC B1545 or B1546 is set in the SRS-ECU,
always diagnose the CAN main bus line.
.
CIRCUIT OPERATION
The load data from the occupant classification sen-
sor is classified with the occupant classification-ECU,
and its classified information is send to SRS-ECU.
The SRS-ECU determines the air bag deployment
based on this classified information, and controls the
power supply circuit to the inflator.
.
DTC SET CONDITIONS
These DTCs are set if communication between the
occupant classification-ECU and the SRS-ECU is not
possible or communication is faulty.
.
TROUBLESHOOTING HINTS
• Damaged wiring harnesses or connectors
• Malfunction of the occupant classification-ECU
• Malfunction of the SRS-ECU
.
DIAGNOSIS
Required Special Tools:
• MB991958: Scan 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)
AC305415
CONNECTORS : C-211, C-215
C-211
C-215
AZ
AC308166
CONNECTOR : D-30
AB
D-30 (GR)
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-323
STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.
CAUTION
To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958. Refer to "How to connect the
scan 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,
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 ).
AC305412
AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
AC305412
AB
MB991910
DATA LINK
CONNECTOR
MB991824
MB991827
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-324
STEP 3. Measure the resistance at occupant
classification-ECU connector D-30.
(1) Disconnect the connector D-30.
(2) Check for continuity between D-30 harness side connector
terminals 1 and body ground.
It should be 2 ohms or less.
Q: Is the measured resistance 2 ohms or less?
YES : Then go to Step 4.
NO : Repair the wiring harness between occupant
classification-ECU connector D-30 terminals 1 and
the body ground. Then go to Step 8.
STEP 4. Measure the voltage at occupant
classification-ECU connector D-30.
(1) Disconnect the connector D-30.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 2 and ground. It
should measure approximately 12 volts (battery positive
voltage).
Q: Is battery positive voltage (approximately 12 volts)
present?
YES : Go to Step 5.
NO : Go to Step 8.
AC308166
CONNECTOR : D-30
AC
D-30 (GR)
HARNESS SIDE
AC308191AB
D-30 HARNESS SIDE
CONNECTOR
AC308166
CONNECTOR : D-30
AC
D-30 (GR)
HARNESS SIDE
AC308192AB
D-30 HARNESS SIDE
CONNECTOR
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-325
STEP 5. Check the harness wires for open circuit or short
circuit between occcupant classification-ECU connector
D-30 (terminal No.2) and ignition switch connector C-308
(terminal No.2).
AC308166
CONNECTOR : D-30
AC
D-30 (GR)
HARNESS SIDE
AC305235AG
CONNECTOR: C-308
C-308
2
5
4
1
6
3
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