Mitsubishi Montero (2002-2004). Manual - part 1019

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-101

STEP 6. Check the following harness wire.

• The wire between buzzer connector E-107 (terminal 1) and 

junction block connector D-208 (terminal 4)

NOTE: Also check joint connector D-116, intermediate connec-
tor E-111 and junction block connector D-212 for loose, cor-
roded, or damaged terminals, or terminals pushed back in the 
connector. If joint connector D-116, intermediate connector E-
111 or junction block connector D-212 is damaged, repair or 
replace the damaged component(s) as described in GROUP 
00E, Harness Connector Inspection 

P.00E-2

. If the connector 

has been repaired or replaced, go to Step 7.

AC204727AB

CONNECTOR: E-107

E-107

HARNESS 
CONNECTOR: 
COMPONENT 
SIDE

E-107

AC204624 AC

CONNECTOR: D-208

D-208

JUNCTION BLOCK
(FRONT VIEW)

D-208 JUNCTION BLOCK
CONNECTOR

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-102

Q: Is the harness wire damaged?

YES : Repair it and then go to Step 7.
NO :  Go to Step 7.

AC204689 AB

CONNECTOR: D-116

D-116

D-116

JOINT CONNECTOR (4): 
JOINT PIN SIDE

AC204548AK

CONNECTOR: E-111

E-111

AC204624 AD

CONNECTOR: D-212

D-212

JUNCTION BLOCK
(FRONT VIEW)

HARNESS CONNECTOR: 
COMPONENT SIDE

3

4

10

11

8

9

1

2

5

6

7

D-212

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-103

STEP 7. Retest the system.
(1) Apply a chock to the wheel.
(2) Start the engine.
(3) When 120 seconds or more have been elapsed since the 

engine was started, release the parking brake lever and 
fully depress the brake pedal repeatedly 15 to 20 times 
within 10 seconds.

Q: Does the buzzer sound? 

YES : The procedure is complete.
NO :  Start over at Step 1.

INSPECTION PROCEDURE 4: The Buzzer does not Stop Sounding.

NOTE: This diagnosis procedure is limited to cases where communication with the scan tool is possible (M-
ASTC-ECU power supply is normal) and no DTC sets.

.

CIRCUIT OPERATION

• The M-ASTC-ECU and the transfer-ECU controls 

the buzzer by turning the power transistor in the 
ECU ON and OFF.

• The M-ASTC-ECU outputs the buzzer-sounding 

signal when an abnormality occurs on the 
hydraulic brake booster. (And at the same time, 
the M-ASTC-ECU turns on the brake warning 
light.)

AC204503AB

Brake Warning Light Circuit

AC204548AI

CONNECTORS: E-104, E-107, E-114

E-104

E-107

E-114

AC203901AF

CONNECTOR: E-120

E-120

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-104

• The transfer-ECU outputs the buzzer-sounding 

signal when an abnormality occurs on the active 
trac 4WD II system.

.

TECHNICAL DESCRIPTION (COMMENT)
The cause is probably an M-ASTC-ECU or transfer-
ECU malfunction.

.

TROUBLESHOOTING HINTS

• Damaged wiring harness or connector

• Malfunction of the M-ASTC-ECU

• Malfunction of the transfer-ECU

• Malfunction of the buzzer

.

DIAGNOSIS

Required Special Tool:

• MB991502: Scan Tool (MUT-II)

STEP 1. Check the buzzer circuit at M-ASTC-ECU 
connector E-120.
Disconnect M-ASTC-ECU connector E-120.
Q: Does the buzzer still keep on sounding?

YES : Go to Step 2.
NO :  Replace the M-ASTC-ECU (Refer to GROUP 35C, M-

ASTC-ECU 

P.35C-205

). Then go to Step 5.

AC203901

AC204627AE

CONNECTOR: E-120

M-ASTC-ECU CONNECTOR

E-120

E-120