Mitsubishi Montero (2004+). Manual — part 1021

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-83

HBB SYMPTOM PROCEDURES

INSPECTION PROCEDURE 1: The Brake Warning Light does not Illuminate when the Ignition Switch
is Turned to the "ON" Position just after the Engine Start.

AC204500AB

Brake Warning Light Circuit

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-84

.

CIRCUIT OPERATION

• The brake warning light power is supplied from

the ignition switch (IG1). The M-ASTC-ECU
grounds the circuit to illuminate the brake warn-
ing light.

• The M-ASTC-ECU illuminates the brake warning

light for 3 seconds while running its self-check.
The brake warning light can be illuminated for 3
seconds upon start-up or with the ignition switch
in the "ON" position, and the engine stopped.

.

TECHNICAL DESCRIPTION (COMMENT)
The cause is probably an open circuit at the brake
warning light circuit, or malfunction of the
M-ASTC-ECU.

.

TROUBLESHOOTING HINTS

• Damaged wiring harness or connector

• Blown fuse

• Malfunction of the combination meter

• Malfunction of the M-ASTC-ECU

.

DIAGNOSIS

Required Special Tool:

• MB991223: Harness Set

STEP 1. Check whether the brake warning light
illuminates.
Q: Does the brake warning light illuminate at the condition

that the ignition switch is turned to the "ON" position
and the engine is stopped.
YES : Go to Step 2.
NO : Go to Step 5.

AC204687AB

CONNECTORS: D-03, D-30

D-03 (GR)

D-30

AC204547AC

CONNECTORS: D-208, D-210

D-208

D-210

JUNCTION BLOCK
(FRONT VIEW)

AC204548 AB

CONNECTOR: E-111

E-111

AC203901AG

CONNECTOR: E-121

E-121

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-85

STEP 2. Check the brake warning light circuit at
M-ASTC-ECU connector E-121.

(1) Disconnect M-ASTC-ECU connector E-121.
(2) Turn the ignition switch to the "ON" position.
(3) Check whether the brake warning light is illuminated. The

brake warning light should illuminate.

Q: Does the brake warning light illuminate?

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

M-ASTC-ECU

P.35C-213

). and then go to Step 9.

NO : Go to Step 3.

AC203901

AC204627AP

CONNECTOR: E-121

M-ASTC-ECU CONNECTOR

E-121

E-121

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-86

STEP 3. Check the following connectors.

• Combination meter connector D-03

• M-ASTC-ECU connector E-121

Check connectors for loose, corroded or damaged terminals, or
terminals pushed back in the connector.
Q: Is any of the connector damaged?

YES : Repair the faulty connector or terminal and then go to

Step 9.

NO : Go to Step 4.

AC204690 AB

COMBINATION METER
CONNECTOR

D-03

CONNECTOR: D-03

D-03 (GR)

AC203901

AC204627AP

CONNECTOR: E-121

M-ASTC-ECU CONNECTOR

E-121

E-121