Mitsubishi Montero (2002-2004). Manual — part 1002

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-33

DIAGNOSIS

Required Special Tool:

• MB991223: Harness Set

STEP 1. Check for any diagnostic trouble code.
(1) Erase the DTC memory.
(2) Check for any diagnostic trouble code.
Q: Is DTC 55 set?

YES : Carry out the troubleshooting for DTC 55 (Refer to

P.35A-56

). Then go to Step 25.

NO : Go to Step 2.

STEP 2. Check the pump motor operation.
(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.

(2) Turn the ignition switch to the "ON" position.
Q: Does the pump motor operate?

YES : Go to Step 22.
NO : Go to Step 3.

STEP 3. Check the motor relay A.

CAUTION

Apply battery voltage according to the table below. Never
confuse the positive and negative battery terminals, or the
diode inside the relay will be damaged.

Q: Is the relay damaged?

YES : Replace the relay. Then go to Step 25.
NO : Go to Step 4.

BATTERY
CONNECTION

TESTER
CONNECTION

SPECIFIED
CONDITION

−

4

− 5

Open circuit

• Connect battery

terminal (+) to
terminal 3

• Connect battery

terminal (

−) to

terminal 1

4

− 5

Less than 2 ohms

AC204381

4

1

3

5

AC204329

ACX01808

AC

BRAKE FLUID
RESERVOIR

MOTOR
RELAY A

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-34

STEP 4. Check the motor relay B.

CAUTION

Apply battery voltage according to the table below. Never
confuse the positive and negative battery terminals, or the
diode inside the relay will be damaged.

Q: Is the relay damaged?

YES : Replace the relay. Then go to Step 25.
NO : Go to Step 5.

BATTERY
CONNECTION

TESTER
CONNECTION

SPECIFIED
CONDITION

−

4

− 5

Open circuit

• Connect battery

terminal (+) to
terminal 3

• Connect battery

terminal (

−) to

terminal 1

4

− 5

Less than 2 ohms

AC204381

4

1

3

5

AC204329

ACX01808

AD

MOTOR
RELAY B

BRAKE FLUID
RESERVOIR

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-35

STEP 5. Check the following connectors.

• Motor relay A connector B-53X

• Motor relay B connector B-54X

• HBB connectors B-17 and B-18

Check connectors, for loose, corroded or damaged terminals,
or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?

YES : Go to Step 6.
NO : Repair the faulty connector or terminal. Then go to

Step 25.

AC204551

3 2 1

5 4

1 2 3

4 5

RELAY BOX CONNECTOR

AB

CONNECTORS: B-53X, B-54X

B-53X

B-54X

AC204629 AB

CONNECTORS: B-17, B-18

B-17 (GR)

B-18 (B)

B-17

B-18

HBB CONNECTORS

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-36

STEP 6. Check the power supply circuit at motor relay A
harness connector B-53X.
(1) Remove the motor relay A.

(2) Measure the voltage between terminal 5 and ground. The

voltage should measure approximately 12 volts (battery
positive voltage).

Q: Is battery positive voltage (approximately 12 volts)

present?
YES : Go to Step 7.
NO : Go to Step 10.

AC204329 AD

MOTOR
RELAY A

AC204552

3 2 1

5 4

1 2 3

4 5

RELAY BOX CONNECTOR

AB

CONNECTOR: B-53X

B-53X