Mitsubishi Montero (2004+). Manual - part 1176

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-39

.

TROUBLESHOOTING HINTS
Malfunction of the SRS-ECU.

.

DIAGNOSIS
Replace the SRS-ECU (Refer to 

P.52B-215

). 

31

Capacitor

• Voltage at the capacitor terminal is higher than the 

specified value for five seconds or more

32

• Voltage at the capacitor terminal is lower than the 

specified value for five seconds or more (This is not 
detected if DTC No.41 or 42 indicating battery positive 
voltage drop has been output).

45

Non-volatile memory (EEPROM) 
and A/D converter

• When the non-volatile memory (EEPROM) and A/D 

converter system are abnormal

51

Driver's air bag module (squib 
ignition drive circuit)

• Short circuit in the squib ignition drive circuit

52

• Open circuit in the squib ignition drive circuit

54

Front passenger's air bag module 
(squib ignition drive circuit)

• Short circuit in the squib ignition drive circuit

55

• Open circuit in the squib ignition drive circuit

56

Driver’s seat belt pre-tensioner 
(squib ignition drive circuit)

• Short circuit in the squib ignition drive circuit

57

• Open circuit in the squib ignition drive circuit

58

Passenger’s seat belt 
pre-tensioner (squib ignition drive 
circuit)

• Short circuit in the squib ignition drive circuit

59

• Open circuit in the squib ignition drive circuit

73

Side-airbag module (RH) (squib 
ignition drive circuit)

• Short circuit in the squib ignition drive circuit

74

• Open circuit in the squib ignition drive circuit

83

Side-airbag module (LH) (squib 
ignition drive circuit)

• Short circuit in the squib ignition drive circuit

84

• Open circuit in the squib ignition drive circuit

CODE NO. DEFECTIVE PART

SYMPTOMS

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-40

DTC 21: Driver’s Air Bag Module (Squib) System Fault 1 (Short Circuit between Terminals of the Squib 
Circuit)

.

AIR BAG MODULE
(SQUIB)
(DRIVER'S SIDE)

CLOCK 
SPRING

MICROCOMPUTER

AIR BAG DRIVE CIRCUIT

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

NOTE

: CONNECTOR
  COUPLED: ON
  CONNECTOR
  UNCOUPLED: OFF

Driver's Air Bag Module (Squib) Circuit 

AC204226AD

CLOCK SPRING

D-206 (Y)

CONNECTORS: D-206, D-229

D-229

ACX01478 AG

CONNECTOR: E-08

E-08 (Y)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-41

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 outputs 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 the followings: 

• Short circuit in driver’s air bag module (squib) 

or harness

• Short circuit in the clock spring

However, if no DTC resets, the SRS warning light will 
be switched off (DTC will be retained). 

.

TROUBLESHOOTING HINTS

• Improper engaged connector or defective short 

spring*

• Short circuit in the clock spring

• Short circuit between the driver's air bag module 

(squib) circuit terminals

• Damaged connector(s)

• Malfunction of the SRS-ECU

.

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-20

). Therefore, if connector E-08, 

D-206 or D-229 is damaged or improperly engaged, 
the short spring may not be released when the con-
nector is connected. 

.

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 (Vehicles without 

CAN communication system)

• MB991865: Dummy resister

• MB991866: Resister harness

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-42

STEP 1. Using scan tool MB991958, read the diagnostic 
trouble code.

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) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOOK (OFF)" position.
Q: Is DTC 34 set?

YES : Go to Step 2.
NO :  Go to Step 3.

STEP 2. Check SRS-ECU connector E-08.
Q: Is the connector correctly engaged?

YES : Go to Step 3.
NO :  Engage the connector correctly. Then go to Step 8.

AC307591 AB

MB991911

DATA LINK

CONNECTOR

MB991824

MB991827

ACX01478AM

CONNECTOR: E-08

E-08 (Y)

HARNESS SIDE
CONNECTOR
(REAR VIEW)