Mitsubishi Galant (2004+). Manual - part 1545

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-73

CAUTION

If DTC B1407 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-airbags should be deployed, it sends a fire sig-
nal to the SRS-ECU to deploy the side-airbags. In
addition, the CPU diagnoses the internal compo-
nents 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 will set when the power supply voltage to
the front impact sensor (RH) remains less than a pre-
determined value for five seconds. However, if the
system returns to normal condition, code number
B1407 will be erased automatically and the SRS
warning light will go out.

TROUBLESHOOTING HINTS

• Damaged wiring harness or connectors

• Malfunction of the front air bag module (RH)

(squib)

• 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)

• MB991223 (MB991222): Harness set (Probe)

AC305233 AO

CONNECTOR: C-22

C-22 (Y)

AC305362

CONNECTOR: C-121

C-121 (Y)

SRS-ECU

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-74

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

P.52B-30

(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

P.54C-14

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 Cope with Intermittent
Malfunction

P.00-6

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305412

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-75

STEP 3. Check the front impact sensor (RH) power supply
circuit. Measure the voltage at the front impact sensor (RH)
connector A-27.
(1) Disconnect the negative battery terminal.

(2) Disconnect front impact sensor (RH) connector A-27, 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-27 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 (RH). (Refer to

P.52B-362

). 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.47

and 48) and front impact sensor (RH) connector A-27
(terminal No.1 and 2).

AC305206

A-27 (Y)

HARNESS SIDE

CONNECTOR: A-27

AC308161

A-27 HARNESS SIDE
CONNECTOR
(REAR VIEW)

AC305362

CONNECTOR: C-121

C-121 (Y)

SRS-ECU

C-121
HARNESS SIDE
CONNECTOR
(REAR VIEW)

AC305206

A-27 (Y)

HARNESS SIDE

CONNECTOR: A-27

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-76

NOTE: After inspecting intermediate connectors C-22 and C-11
inspect the wiring harness. If the intermediate connectors C-22
and C-11 is damaged, repair or replace it.
Q: Are the harness wires between SRS-ECU connector

C-121 (terminal No.47 and 48) and front impact sensor
(RH) connector A-27 (terminal No.1 and 2) in good
condition?
YES : Erase the diagnostic trouble code memory, and check

the diagnostic trouble code. If DTC B1407 sets,
replace the SRS-ECU (Refer to

P.52B-365

). Then go

to Step 5.

NO : Replace the harness wires between SRS-ECU

connector C-121 and front impact sensor (RH)
connector A-27. 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 B1407 set?

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

AC305233 AI

CONNECTOR: C-22