285

  3   Abnormal ABS operation

Likely Causes

[Description] 

It is in close connection with the

driver status and the road conditions and is

difficult to diagnose. However, if there is no

DTC memory, the following inspections can be

performed.

  Improperly installed sensor

  Sensor wire harness faulty

  Damaged sensor

  Damaged ring gear

  Foreign objects in the sensor

  Damaged wheel bearing

  Damaged ABS HCU

  Damaged ABS ECU

Is the sensor installed correctly

Check the sensor output volt-

age

 

 

Check each sensor

Check each sensor ring gear

Check the wheel bearing clearance

 

 

 

Check the ABS ECU socket and

the middle connector

No

Installed it correctly

Abn.

Abn.

Abn.

Abn.

  Ok

  Yes

  No

  Ok

  Ok

Replace

Replace

Repair

the connector

Use scan meter for HCU di-

agnosis

 

  Yes

 

Does the fault reoccur?

  Yes

No

Refer to

"Occasional

Problem

Service Key

Points"

Replace the ABS HCU

Remove the ABS ECU connector,

check whether the resistances

among the following terminals are

within specification?

Standard: 1.0~1.3K ¸

Shake the sensor wire harness and

connector while measuring them

LF: 1-2

RF: 19-20

LR: 5-6

RR: 22-23

Abn.

Replace

or Repair

 

  Yes

Ok

Repair the

wire har-

ness or

connecto

Replace the ABS HCU

Abn.

286

  4    Excessively long brake pedal stroke

Likely Causes

[Description]

 Visually inspect whether there

is leakage or mechanical fault. Use bleeding

method to check whether there is air in the

system. Use the HCU function of the scan

meter to test whether the normally-closed valve

is leaking.

  Brake fluid leakage

  Air in the system

  Brake disc severely worn

  Brake fluid level switch faulty

Tighten the pipe connector as

specified

Visually inspect whether the hydraulic pipe connector is

leaking

 

Check the brake disc wear

Replace the brake disc

Abn.

Ok

  Abn.

 

Check the brake fluid level switch

Ok

 

Bleed and check

Ok

 

Use the scan meter HCU to diagnose and check the nor-

mally-closed valve seal

Ok

Replace the brake fluid level

switch

Abn.

Re-bleed the system

Abn.

Replace the HCU

Abn.

287

  5   The Pedal must be depressed heavily

Likely Causes

[Description]

 Use traditional method to check

the booster and the brake pedal stroke. Scan

meter HCU function can be used to check the

fault of the normally-open valve

   Boost faulty

   Normally-close valve faulty

Replace the HCU

Use Scan meter HCU function can be used to check the

normally-open valve

 

Check the booster and the pedal stroke with Non-ABS tra-

ditional method

Ok

Abn.

288

   

  6   No DTC output（can not
communicate with the scan meter

）

Likely Causes

 [Description]

 It may be the ABS ECU power

supply circuit or diagnosis wire circuit that can

not communicate with the scan meter

  Burned fuse

  Diagnosis wire broken or connector disconnected

  Damaged ABS ECU

  Scan meter faulty

Can the scan meter commu-

nicate with the MK-20 ABS

ECU on other vehicles?

 

ABS scan meter faulty, check it af-

ter repairing it

Replace

Check the power cable, ground wire

and diagnostic wire in the diagnos-

tic interface

 

 

 

Check the diagnostic interface or wire harness

No

  Yes

  No

  Yes

  Continuity

Check ABS power supply

fuse

 

 Ok

Replace the ABS ECU

Repair the

diagnostic

interface or

harness

Is there any scan meter

Abn.

Remove the ABS ECU

connector, check whether

there is continuity between

terminal 7 in the ABS wire

harness and the terminal 8 in

the diagnostic interface

Abn.

No

No