Mitsubishi Montero (2004+). Manual — part 1005

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

TSB Revision

BASIC BRAKE SYSTEM

35A-19

.

CIRCUIT OPERATION
The M-ASTC-ECU has two power supply lines. An
M-ASTC-ECU power is supplied to the
M-ASTC-ECU (terminal 9) from the ignition switch
(IG2) through the multi-purpose fuse number 17 in
the junction block. The other M-ASTC-ECU power is
supplied to the M-ASTC-ECU (terminal 63) from the
ignition switch (IG2) through the multi-purpose fuse
number 5 in the junction block and through the joint
connector number 4.

.

HBB DTC SET CONDITIONS
DTC16 is set if the voltage at both of the power line is
extremely low or high.

.

TROUBLESHOOTING HINTS

• Malfunction of the battery

• Malfunction of the charging system

• Malfunction of the M-ASTC-ECU

.

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface

(V.C.I.)

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B

STEP 1. Check the battery.

Refer to GROUP 54A, Battery

− On-vehicle Service

− Battery Testing Procedure

P.54A-6

.

Q: Is the battery damaged?

YES :

Charge or replace the battery and then go

to Step 4.

NO :

Go to Step 2.

STEP 2. Check the charging system.
Refer to GROUP 16, Charging System

− Diagnosis

P.16-3

.

Q: Is the charging system damaged?

YES :

Repair the Charging System and then go to

Step 4.

NO :

Go to Step 3.

STEP 3. Recheck for diagnostic trouble code.
(1) Erase the DTC memory.
(2) Recheck for diagnostic trouble code.

Q: Is DTC 16 set?

YES :

Replace the M-ASTC-ECU (Refer to

GROUP 35C, M-ASTC-ECU

P.35C-213

).

Then go to Step 4.

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 4. Recheck for diagnostic trouble code.
(1) Erase the DTC memory.
(2) Recheck for diagnostic trouble code.

Q: Is DTC 16 set?

YES :

Start over at Step 1.

NO :

The procedure is complete.

AC204548 AB

CONNECTOR: E-111

E-111

AC203901AD

CONNECTORS: E-119, E-120

E-119

E-120

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-20

DTC 31: Ignition Switch B Circuit (Open Circuit at the HBB Power Supply Sub Circuit)

.

CIRCUIT OPERATION
In the ignition switch B circuit, the M-ASTC-ECU
power is supplied to the M-ASTC-ECU (terminal 9)
from the ignition switch (IG2) through the multi-pur-
pose fuse number 17 in the junction block.

.

HBB DTC SET CONDITIONS
DTC31 is set if the ignition switch B circuit is open or
the internal circuit of the M-ASTC-ECU is defective.

.

TROUBLESHOOTING HINTS

• Damaged wiring harness or connector

• Malfunction of the M-ASTC-ECU

.

AC204493 AB

HBB Power Supply Sub Circuit

AC204548 AB

CONNECTOR: E-111

E-111

AC203901AE

CONNECTOR: E-119

E-119

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-21

DIAGNOSIS

Required Special Tool:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B

• MB991223: Harness Set

STEP 1. Check the following connector.

• M-ASTC-ECU connector E-119

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

YES : Go to Step 2.
NO : Repair it and then go to Step 5.

AC203901

AC204627 AB

CONNECTOR: E-119

E-119

M-ASTC-ECU CONNECTOR

E-119

HYDRAULIC BRAKE BOOSTER (HBB) DIAGNOSIS

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BASIC BRAKE SYSTEM

35A-22

STEP 2. Check the power supply circuit at M-ASTC-ECU
harness connector E-119.

(1) Disconnect M-ASTC-ECU connector E-119 and measure at

the harness connector (component side).

(2) Start the engine.

(3) Measure the voltage between terminal 9 and ground. It

should measure approximately 12 volts (battery positive
voltage).

Q: Is battery positive voltage (approximately 12 volts)

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

AC203901

AC204627 AB

CONNECTOR: E-119

E-119

M-ASTC-ECU CONNECTOR

E-119

AC204549AC

HARNESS CONNECTOR:
COMPONENT SIDE

E-119