Mitsubishi Montero (2002-2004). Manual - part 999

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-21

STEP 3. Check the following harness wire.

• The wire between M-ASTC-ECU connector E-119 (terminal 

9) and multi-purpose fuse number 17 (junction block)
NOTE:  Also check intermediate connector E-111 for loose, 
corroded, or damaged terminals, or terminals pushed back 
in the connector. If intermediate connector E-111 is dam-
aged, 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 5.

Q: Is the harness wire damaged?

YES : Repair or replace it and then go to Step 5.
NO :  Go to Step 5.

AC203901

AC204627AC

CONNECTOR: E-119

E-119

HARNESS CONNECTOR: 
COMPONENT SIDE

E-119

AC203896AE

AC203896

MULTIPURPOSE FUSE NO.17

JUNCTION 
BLOCK

MULTIPURPOSE 
FUSE NO.17

AC204548AK

CONNECTOR: E-111

E-111

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-22

STEP 4. Recheck for diagnostic trouble code.
(1) Erase the DTC memory.
(2) Recheck for diagnostic trouble code.
Q: Is DTC 31 set?

YES : Replace the M-ASTC-ECU (Refer to GROUP 35C, M-

ASTC-ECU 

P.35C-205

). Then go to Step 5.

NO :  It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use Troubleshooting/
Inspection Service Points 

− How to Cope with 

Intermittent Malfunction 

P.00-6

.

STEP 5. Recheck for diagnostic trouble code.
(1) Erase the DTC memory.
(2) Recheck for diagnostic trouble code.
Q: Is DTC 31 set?

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

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-23

DTC 53: Pump Motor (Seizure of the Pump Motor or Abnormality at the Current Detecting Circuit of 
the M-ASTC-ECU)

AC204494 AB

Pump Motor Circuit

AC204545 AC

CONNECTORS: B-17, B-18

B-17 (GR)

B-18 (B)

AC204329 AC

CONNECTORS: B-53X, B-54X

B-53X

B-54X

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-24

.

CIRCUIT OPERATION

• The pump motor operates if the motor relay A or 

motor relay B turn to ON. 

• The M-ASTC-ECU monitors the pump motor (at 

25 terminal). 

• The M-ASTC-ECU monitors the power supply 

current for the pump motor at 14 terminal, and 
ground current at 12 terminal, respectively, to 
know whether the pump motor is locked or not. 

.

HBB DTC SET CONDITIONS
DTC 53 will be set when the pump motor is locked, 
two ground lines are open circuit or poorly grounded, 
or the current monitoring circuit is defective. If the 
pump motor has been locked, the M-ASTC-ECU 
sounds the buzzer continuously to inform the trouble 
of the driver and protects the pump motor by activat-
ing it intermittently.

.

TROUBLESHOOTING HINTS

• Malfunction of the pump motor [Integrated with 

the hydraulic brake booster (HBB)]

• Damaged wiring harness or connector

• Malfunction of the M-ASTC-ECU

• Malfunction of the master cylinder and hydraulic 

unit assembly [Integrated with the hydraulic brake 
booster (HBB)]

.

DIAGNOSIS

Required Special Tool:

• MB991223: Harness Set

STEP 1. Check the sound of the HBB buzzer.
Q: Does the HBB buzzer sound?

YES : Check the pump motor for seizure, and replace the 

pump motor if necessary. Then go to Step 10.

NO :  Go to Step 2.

AC203901AE

CONNECTOR: E-119

E-119