Mitsubishi Montero Sport (2004+). Manual — part 741

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-33

CIRCUIT OPERATION

• The SRS-ECU judges how severe a collision is

by detecting signals from the left and right front
impact sensors and the analog G-sensor. If the
impact is over a predetermined level, the
SRS-ECU outputs an ignition signal. At this time,
if the 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 CONDITION

• These DTC's are set if there is abnormal resis-

tance between the input terminals of the driver's
side air bag module (squib).

• The most likely causes for this code to be set are

shown in the table below:

.

NOTE: *: The squib circuit connectors integrate a "short" spring (which prevents the air bag from deploying
unintentionally due to static electricity by shorting the positive wire to the ground wire in the squib circuit when
the connectors are disconnected) (Refer to

P.52B-21

.) Therefore, if the connector (C-24, and D-18 and D-20)

are damaged or improperly engaged, the short spring may not be released when the connector is connected.

.

TROUBLESHOOTING HINTS

• Improper engaged connector or defective short

spring*

• Malfunction of the clock spring

• Half-open circuit caused by improper clock spring

neutral position

• Damaged wiring harnesses or connectors

• Malfunction of the driver's side air bag module

(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

• MB991911: MUT-III Main Harness B

• MB991865: Dummy resister

• MB991866: Resister harness

DTC

SYMPTOM

21

• Short circuit in driver's side air bag module (squib) or harness

• Short circuit in clock spring

22

• Open circuit in driver's side air bag module (squib) or harness

• Open circuit in clock spring

• Disconnection of driver's side air bag module (squib) connector

• Half-open circuit caused by improper clock spring neutral position

• Malfunction of connector contact

61

• Short circuit in driver's side air bag module (squib) harness leading to

the power supply

62

• Short circuit in driver's side air bag module (squib) harness leading to

the ground

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-34

STEP 1. Check the clock spring connector D-20.

Remove the air bag module mounting equipment and check
clock spring connector D-20. At this time, check that there is
no gap at place B shown in the illustration.

Q: Is the connector correctly connected?

YES : Go to Step 2.
NO : Insert the connector to the place, where there remains

no gap at place B shown in the illustration. Then go to
Step 5.

STEP 2. Check the clock spring line. (Using scan tool
MB991958, read the diagnostic trouble code.)

(1) Release the clock spring connector (2-pin) D-18.
(2) Connect the dummy resistor (MB991865) to the resistor

harness (MB991866).

CAUTION

Do not directly insert a probe or other devices at the front
of the connector to avoid a possible decrease in the con-
tact pressure.
(3) Insert the resistor harness (MB991866) behind the harness

side connector D-18.

(4) Connect the negative (

−) battery terminal.

(5) Erase the diagnostic trouble code memory. Then check the

diagnostic trouble code again.

Q: Is any of DTC 21, 22, 61 or 62 set?

YES : Go to Step 4.
NO : Go to Step 3.

STEP 3. Check the clock spring.
(1) Check the connectors and protective tube for damaged,

and the terminal for deformation.

(2) Visually check the case for damaged.
Q: Is any malfunction found on the clock spring?

YES : Replace the clock spring (Refer to

P.52B-84

.) Then

go to Step 5.

NO : Replace the driver's side air bag module. (Refer to

P.52B-84

.) Then go to Step 5.

AC002016

A

A

B

CLOCK SPRING
CONNECTOR: D-20

INFLATOR CASE

AF

AC102572 AH

DUMMY
RESISTOR (3

Ω)

(MB991865)

RESISTOR
HARNESS
(MB991866)

HARNESS SIDE
CONNECTOR

D-18 CLOCK SPRING
CONNECTOR

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-35

STEP 4. Check the harness wires between SRS-ECU
connector C-24 (terminal No.11, 12) and clock spring
connector D-18 (terminal No.1 and 2).

Q: Are the harness wires between SRS-ECU connector

C-24 (terminal No.11and 12) clock spring connector
D-18 (terminal No.1 and 2) in good condition?
YES : Go to Step 5.
NO : Repair or replace the harness wires between

SRS-ECU connector C-24 and clock spring connector
D-18. Then go to Step 5.

STEP 5. Recheck for diagnostic trouble code.
Q: Is any of DTC 21, 22, 61 or 62 set?

YES : Return to Step 1.
NO : The procedure is complete. (If no malfunctions are

found in all steps, an intermittent malfunction is
suspected. Refer to GROUP 00, How to Use
Troubleshooting/Inspection Service Points

− How to

Cope with Intermittent Malfunction

P.00-7

.)

AC202743

20

19

18

17

7

15

8

16

6

5

4

12

13 14

3

2

1

9 10 11

CONNECTOR: C-24

C-24 (Y)

C-24 HARNESS CONNECTOR:
HARNESS SIDE
(REAR VIEW)

AD

SRS-ECU

AC200755

1 2

CONNECTOR: D-18

D-18 HARNESS
CONNECTOR:
HARNESS SIDE
(REAR VIEW)

AC

D-18 (R)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-36

DTC 24: Passenger (Front) Side Air Bag Module (Squib) System Fault 1 DTC 25: Passenger (Front)
Side Air Bag Module (Squib) System Fault 2 DTC 64: Passenger (Front) Side Air Bag Module (Squib)
System Fault for Power Supply Circuit DTC 65: Passenger (Front) Side Air Bag Module (Squib)
System Fault for Ground Circuit

CIRCUIT OPERATION

• The SRS-ECU judges how severe a collision is

by detecting signals from the left and right front
impact sensors and the analog G-sensor. If the
impact is over a predetermined level, the
SRS-ECU outputs an ignition signal. At this time,
if the safing G-sensor is on, the SRS air bag will
inflate.

• The ignition signal is input to the air bag module

to inflate the air bag.

Passenger's Side Air Bag Module Squib Circuit

AC003288

CONNECTOR: C-24

AE

SRS-ECU

C-24 (Y)

AC003296

CONNECTOR: C-49

AD

C-49 (R)