Mitsubishi Evolution X. Manual - part 728

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-359

Inspection procedure 2: Power supply circuit system

.

ETACS-ECU

FUSIBLE
LINK

34

IGNITION
SWITCH (IG1)

IG1
RELAY

SRS-ECU

POWER 
SUPPLY

IG1 Power Supply Circuit

JOINT CONNECTOR (4)

JOINT CONNECTOR (5)

AC708951BY

C-37 (Y) C-36 (Y)

Connector:s C-36, C-37

AC708972AN

Connectors: C-309, C-313, C-317

Junction block

C-317

C-309 (B)

C-313 (BR)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-360

CIRCUIT OPERATION

• The SRS-ECU is energized by the ignition switch 

(IG1) through multi-purpose fuse 18 and the 
SRS-ECU terminal 61 and multi-purpose fuse 12 
and the SRS-ECU terminal 62.

• If the power supply to the SRS-ECU has failed, 

scan tool (M.U.T.-III Sub Assembly) will not be 
able to communicate with it.

.

TROUBLESHOOTING HINTS (THE MOST 
LIKELY CAUSES FOR THIS CASE:) 

• Damaged wiring harness or connector

• Defective battery

• Charging system failed

• Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A (Vehicles with 

CAN communication system)

STEP 1. Resistance measurement at the C-37 SRS-ECU 
connectors
(1) While pushing the part "A" indicated in the figure of the 

harness side connector, turn the lock lever to the direction 
of the arrow to release the lock lever, and disconnect the 
C-37 SRS-ECU connectors.

(2) Take the measurements below at the C-37 wiring harness 

side connectors. 

• Continuity between C-37 wiring harness side connector 

terminal No. 17 and body ground

OK: Continuity (Less than 2 ohms)

Q: Is the check result normal?

YES : Go to Step 2.
NO :  Repair the wiring harness between the C-37 

SRS-ECU connector terminal No. 17 and body 
ground.

STEP 2. Wiring harness check between the C-36 SRS-ECU 
connector terminal Nos. 61 and 62 and the ignition switch 
IG1
NOTE: Prior to the wiring harness inspection, check the 
ETACS-ECU connectors C-309, C-313 and C-317, and repair if 
necessary.

• Check the power supply line for open and short circuit.

Q: Is the check result normal?

YES : Go to Step 3.
NO :  Repair the wiring harness.

AC506734

A

AD

Lock lever

AC608812

C-37 Harness side 
connector (front view)

HC

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-361

STEP 3. Retest the system
Q: Is the communication between scan tool and SRS-ECU 

possible?
YES : Intermittent malfunction (Refer to GROUP 00, How to 

Use Troubleshooting/Inspection Service Points 

−How 

to Cope with Intermittent Malfunction 

P.00-15

.)

NO :  Replace SRS-ECU (Refer to 

P.52B-383

).

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-362

Inspection procedure 3:The SRS Warning Light does not Illuminate.

ETACS-ECU

COMBINATION METER

CPU

FUSIBLE
LINK

34

CAN DRIVE
CIRCUIT

IGNITION
SWITCH (IG1)

IG1
RELAY

INTERFACE
CIRCUIT

CAN TRANSCEIVER 
CIRCUIT

LED DRIVE 
CIRCUIT

JOINT CONNECTOR
(CAN1)

SRS-ECU

SRS Warning Light Circuit