Mitsubishi Montero (2002-2004). Manual - part 1013

 

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Mitsubishi Montero (2002-2004). Manual - part 1013

 

 

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-77

STEP 8. Recheck for diagnostic trouble code.
(1) Erase the DTC memory.
(2) Recheck for diagnostic trouble code.
Q: Is DTC 56 set?

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

DTC 57: Accumulator (Accumulator Low-Pressure Abnormality)

.

CIRCUIT OPERATION
The pressure switch (for low-pressure warning) mon-
itors brake fluid pressure inside of the hydraulic 
brake booster (HBB). When the brake fluid pressure 
decreases abnormally, the pressure switch (for low-
pressure warning) is turned off and the brake fluid 
low-pressure warning signal is output to the M-
ASTC-ECU. 

.

HBB DTC SET CONDITIONS
DTC 57 is set if the brake fluid pressure decreases, 
or the pressure switch (for low-pressure warning) 
OFF seize-up occurs. In this case, the M-ASTC-ECU 
sounds the buzzer continuously to inform the trouble 
of the driver and protects the pump motor by activat-
ing the pump motor intermittently.

.

AC204498AB

Pressure Switch (for Low-Pressure Warning) Circuit

AC204545AB

CONNECTOR: B-17

B-17 (GR)

AC203901AF

CONNECTOR: E-120

E-120

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-78

TROUBLESHOOTING HINTS

• Brake fluid leakage in the hydraulic brake booster 

(HBB)

• Malfunction of the accumulator [Integrated with 

the hydraulic brake booster (HBB)]

• Malfunction of the pressure switch (for low-pres-

sure warning) [Integrated with the hydraulic brake 
booster (HBB)]

.

DIAGNOSIS

Required Special Tool:

• MB991223: Harness Set

STEP 1. Check the pressure switch (for low-pressure 
warning) circuit inside the HBB.
(1) Depress the pedal repeatedly more than 40 times until the 

pedal depressing force feels heavy with the ignition switch 
at the "LOCK" (OFF) position to release the pressure of 
HBB power supply system.

(2) Disconnect HBB connector B-17.

(3) Measure the resistance between the terminals 1 and 5 at 

the HBB. The resistance should measure approximately 1 
kilo ohms. 

Q: Is the resistance approximately 1 kilo ohms?

YES : Go to Step 2.
NO :  Replace the master cylinder and hydraulic unit 

assembly (Refer to 

P.35A-136

). Then go to Step 5.

AC204629 AC

CONNECTOR: B-17

B-17 (GR)

HBB CONNECTOR

B-17

AC204686 AB

HBB CONNECTOR

B-17

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-79

STEP 2. Check the leakage of brake fluid from the HBB 
visually.
Q: Is there leakage of brake fluid from the HBB?

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

STEP 3. Disassemble and check the HBB.
(1) Remove the HBB (Refer to 

P.35A-133

).

(2) Disassemble the HBB (Refer to 

P.35A-136

).

(3) Check the HBB for the following points.

• Power piston assembly for rust, damage, wear and 

deterioration

• Master cylinder piston assembly for rust, damage, wear 

and deterioration

• Inside of the hydraulic unit assembly cylinder for rust 

and damage

Q: Are all of the checked items in good condition?

YES : Assemble the HBB (Refer to 

P.35A-136

), install the 

HBB (Refer to 

P.35A-133

), refill the brake fluid, and 

bleed the brake line (Refer to 

P.35A-122

). Then go to 

Step 4.

NO :  Replace the deficient parts, assemble the HBB (Refer 

to 

P.35A-136

), install the HBB (Refer to 

P.35A-133

), 

refill the brake fluid, and bleed the brake line (Refer to 

P.35A-122

). Then go to Step 5.

STEP 4. Recheck for diagnostic trouble code.
(1) Erase the DTC memory.
(2) Recheck for diagnostic trouble code.
Q: Is DTC 57 set?

YES : Replace the accumulator (Refer to 

P.35A-134

). 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 57 set?

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

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-80

SYMPTOM CHART

M1351013200050

NOTE: The hydraulic brake booster (HBB) accumulates the high-pressure oil in the accumulator by the acti-
vation of the pump motor to assist the brake power. Even though the working sound of the pump motor can 
be heard during operation, this sound is usually generated at normal operation of the HBB and is not an indi-
cation of a malfunction.

SYMPTOM

INSPECTION 
PROCEDURE NO.

REFERENCE 
PAGE

Communication between the scan tool and the whole system is 
not possible.

Refer to GROUP 
13A, Diagnosis 

P.13Ad-2

.

Communication between the scan tool and the M-ASTC-ECU is 
not possible.

Refer to GROUP 
35B, Diagnosis 

P.35B-4

.

The brake warning light does not illuminate when the ignition 
switch is turned to the "ON" position just after the engine start.

1

P.35A-81

The brake warning light remains illuminated after the engine is 
started.

2

P.35A-90

DTC 53 <seizure of the pump motor>, DTC 55 or DTC57 is set, 
but he buzzer does not sound. 

3

P.35A-95

The buzzer does not stop sounding.

4

P.35A-103

 

 

 

 

 

 

 

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