Mitsubishi Galant (2004+). Manual — part 533

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

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ANTI-LOCK BRAKING SYSTEM (ABS)

35B-77

DTC C1860/C1861: Power supply system (abnormal decrease or increase in voltage)

CAUTION

If there is any problem in the CAN bus lines, an
incorrect diagnostic trouble code may be set.
Prior to this diagnosis, diagnose the CAN bus
lines.

.

CIRCUIT OPERATION
The ABS-ECU is energized by the ignition switch
(IG1) through multi-purpose fuse 23 and the
ABS-ECU terminal 20.

.

JUNCTION
BLOCK

IGNITION
SWITCH (IG1)

POWER
SUPPLY

ABS-ECU

ABS-ECU Power Supply and Ground Circuit

AC304742

A-02 (GR)

CONNECTOR: A-02

HYDRAULIC UNIT
(WITH BUILT-IN ABS-ECU)

AC

AC305415

CONNECTORS : C-214, C-215

C-214

C-215

AW

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

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ANTI-LOCK BRAKING SYSTEM (ABS)

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ABS DTC SET CONDITIONS
C1861 will be set when the power supply voltage to
the ABS-ECU has decreased to a predetermined
value or lower. C1860 will be set when the power
supply voltage to the ABS-ECU has increased to a
predetermined value or higher.

.

TROUBLESHOOTING HINTS (The most likely
causes for these DTCs are to set are:)

Currect trouble

• Excessive electrical load

• Defective battery

• Damaged wiring harness or connector

• Malfunction of the hydraulic unit (integrated with

ABS-ECU)

• Charging system failed

.

Past trouble
Carry out diagnosis with particular emphasis on con-
nector(s) or wiring harness in the power supply cir-
cuit (terminal 20) to the ABS-ECU. For diagnosis
procedures, refer to "How to cope with past trouble"
(Refer to GROUP 00, How to Use Troubleshoot-
ing/Inspection Service Points

P.00-6

).

.

DIAGNOSIS

Required Special Tools:

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

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

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A

• MB991970: ABS Check Harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus
line.

CAUTION

To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.

(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?

YES : Go to Step 3.
NO : Repair the CAN bus line (Refer to GROUP 54C,

Diagnosis

P.54C-14

). Then go to Step 2.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

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ANTI-LOCK BRAKING SYSTEM (ABS)

35B-79

STEP 2. Recheck for diagnostic trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Turn the ignition switch to the "ON" position.
(2) Erase the DTC.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
(4) Turn the ignition switch to the "ON" position.
(5) Check if the DTC is set.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1860 or C1861 set?

YES : Go to Step 3.
NO : The procedure is complete.

STEP 3. Check the battery.
Check the battery (Refer to GROUP 54A, Battery test

P.54A-7

).

Q: Is the battery in good condition?

YES : Go to Step 4.
NO : Charge or replace the battery. Then go to Step 8.

STEP 4. Check the charging system.

Check the charging system (Refer to GROUP 16, Charging
system diagnosis

P.16-4

).

Q: Is the charging system in good condition?

YES : Go to Step 5.
NO : Repair or replace the charging system component(s).

Then go to Step 8.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

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ANTI-LOCK BRAKING SYSTEM (ABS)

35B-80

STEP 5. Measure the voltage at ABS-ECU connector A-02.

(1) Disconnect the connector A-02, and connect special tool

ABS Check Harness (MB991970) to the wiring
harness-side connector.
NOTE: Do not connect special tool ABS Check Harness
(MB991970) to the ABS-ECU.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 20 and ground. It

should be approximately 12 volts (battery positive voltage).

Q: Is the voltage approximately 12 volts (battery positive

voltage)?
YES : Go to Step 7.
NO : Go to Step 6.

AC306403

19

2

18

1

8

9

7

6

5

4

3

10

11

25

15

16

17

27

28

26

12

13

14

23

24

22 21 20

A-02(GR)

CONNECTOR: A-02

HYDRAULIC UNIT
(WITH BUILT-IN ABS-ECU)

AJ

ABS-ECU

MB991970

CHECK CONNECTOR

A-02 HARNESS
CONNECTOR