Mitsubishi Montero (2002-2004). Manual - part 1059

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

TSB Revision

ANTI-LOCK BRAKING SYSTEM (ABS)

35B-107

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CIRCUIT OPERATION

• The ABS warning light power is supplied from the 

ignition switch. The M-ASTC-ECU grounds the 
circuit to illuminate the light. The light also illumi-
nates when the valve relay is switched to OFF.

• The M-ASTC-ECU illuminates the ABS warning 

light for three seconds while running self-check. 
This light can be illuminated for three seconds 
upon start-up or ignition switch to the "ON" posi-
tion, engine stopped. The M-ASTC-ECU drives 
the valve relay in the order of OFF to ON to OFF 
to ON during initial check to check the valve relay.

.

TECHNICAL DESCRIPTION (COMMENT)
The M-ASTC-ECU causes the ABS warning light to 
illuminate during the initial check (three seconds). 
During the initial check, the valve relay turns from off 
to on, off and back to on again, and if there is a open 
circuit in the harness between the M-ASTC-ECU and 
the ABS warning light, the light will illuminate only 
when the valve relay is OFF because of a valve relay 
test, etc.

.

TROUBLESHOOTING HINTS

• Damaged wiring harness or connector

• Malfunction of the M-ASTC-ECU

.

AC204385

CONNECTORS: E-108, E-110

AE

E-110

E-108(B)

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

TSB Revision

ANTI-LOCK BRAKING SYSTEM (ABS)

35B-108

DIAGNOSIS

Required Special Tool:

• MB991223: Harness Set

STEP 1. Check the ABS warning light circuit at M-ASTC-
ECU connector E-120.
(1) Disconnect M-ASTC-ECU connector E-120 and measure at 

the harness side.

(2) Remove the valve relay.

(3) Ground the terminal 62.
(4) Turn the ignition switch to the "ON" position. The ABS 

warning light should turn on.

Q: Is the ABS warning light turn on?

YES : Replace the M-ASTC-ECU. Then go to Step 3.
NO :  Go to Step 2.

AC204674

AB

B-21X (VALVE RELAY)

CONNECTOR: B-21X

AC203901

AC204627

CONNECTOR: E-120

AS

E-120

HARNESS CONNECTOR:
COMPONENT SIDE

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

TSB Revision

ANTI-LOCK BRAKING SYSTEM (ABS)

35B-109

STEP 2. Check the harness wires between combination 
meter connector D-03 terminal 56 and M-ASTC-ECU 
connector E-120 terminal 62.

AC204690 AC

CONNECTOR: D-03

D-03 (GR)

HARNESS CONNECTOR: 
COMPONENT SIDE

D-03

AC203901

AC204627AG

CONNECTOR: E-120

E-120

HARNESS CONNECTOR: 
COMPONENT SIDE

E-120

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

TSB Revision

ANTI-LOCK BRAKING SYSTEM (ABS)

35B-110

NOTE: After inspecting M-ASTC-ECU connector E-106, 
inspect the wire. If M-ASTC-ECU connector E-106 is damaged, 
repair or replace it. Refer to GROUP 00E, Harness Connector 
Inspection 

P.00E-2

.Then go to Step 3.

Q: Is the harness wire between combination meter 

connector D-03 terminal 56 and M-ASTC-ECU connector 
E-106 terminal 62 damaged?
YES : Repair it and then go to Step 3.
NO :  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 3. Retest the system.
Q: Does the ABS warning light illuminate for 3 seconds 

when the ignition switch is turned to the "ON" position 
with engine stopped or upon start-up?
YES : The procedure is complete.
NO :  Return to Step 1.

INSPECTION PROCEDURE 6: Faulty ABS Operation

.

TECHNICAL DESCRIPTION (COMMENT)
The cause depends on driving and road surface con-
ditions, so diagnosis may be difficult. However, if no 
diagnostic trouble code is displayed, carry out the fol-
lowing inspection.

.

TROUBLESHOOTING HINTS

• Malfunction of the hydraulic brake booster (HBB)

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DIAGNOSIS

Required Special Tool:

• MB991502: Scan tool (MUT-II)

STEP 1. Check the HBB hydraulic unit.
Check the operation of HBB hydraulic unit. Refer to 

P.35B-121

. 

Q: Does HBB hydraulic unit operate normally?

YES : Intermittent malfunction of the vehicle speed sensor is 

assumed to be the cause. Refer to GROUP 00, How 
to Use Troubleshooting/Inspection Service Points 

− 

How to Cope With Intermittent Malfunction 

P.00-6

. 

Then go to Step 2.

NO :  Replace the HBB master cylinder and hydraulic unit 

assembly and go to Step 2. 

STEP 2. Retest the system.
Q: Do the brakes operate normally?

YES : The procedure is complete.
NO :  Return to Step 1.

AC204385

CONNECTOR: E-110

AD

E-110

6

1

7

2

9

8

10

3

5

12

11

4

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