HEXA

Anti-lock Braking System(ABS)

4. TROUBLE SHOOTING AND DIAGNOSIS :

While the key is in IGN position, the ABS ECU

monitors the system for faults. Diagnostic

information and system function monitoring can

be accessed by connecting diagnostic tool to the

vehicle diagnostic connector.

After detecting a fault, the ABS ECU will select a

suitable default strategy which will retain, if

possible, some operational ABS capability. If ABS

is not active, conventional braking will remain

available.

A. ROAD TEST :

WARNING :

It is essential that brake pedal travel is not

obstructed by items such as extra floor mats.

(a) While driving the vehicle with ABS :

Observe the warning lights, check parking

brake/fluid warning light extinguishes after initial

bulb check and when the parking brake is

released, indicating that power assistance is

available.

(b) Normal ABS brake operation :

In road conditions where surface friction is

sufficient to slow or stop the vehicle without wheel

lock, ABS does not operate.

In an emergency braking situation, if one or more

wheels begin to slow rapidly in relation to vehicle

speed, ABS will detect wheel locking tendency

and will regulate brake pressure to maintain wheel

rotation.

(c) Brake application with partial failure :

WARNING :

If a fault develops in the brake system it is

essential that it is investigated immediately.

i. TMC failure :

If during braking, a drastically reduced resistance

is detected at the pedal and braking effectiveness

is very much reduced, failure of the non-powered

(master cylinder) portion of system is indicated. If

this occurs, do not pump the brake pedal. Push

the pedal through free movement to obtain

braking effort from the power circuit.

ii. Brake Booster failure :

When power assistance is not available, braking

effort is only available from the master cylinder In

this case the pedal travel will be or feel shorter as

there is no assistance and greater effort will be

required to stop the vehicle.

WARNING :

Foot pressure on the pedal, using master

cylinder only, will not achieve the same degree of

braking as is available from power assistance.

ii. Insufficient fluid in TMC

If there is insufficient fluid in master cylinder to

create pressure, braking to all four wheels is

retained and ABS remains operative. The red

warning light

(fluid level indicator lamp)

will be

illuminated if the level in fluid reservoir is low

(due

to leakage of fluid)

enough to actuate fluid level

switch.

WARNING :

Longer pedal travel is required, but power

assisted braking is available at reduced efficiency.

B. TABLE OF ABS 9.1 - FALL-BACK LEVEL

ABS

FALLBAC

K LEVEL

ABS Warning

Lamp

Brake Lamp

Status

System

active

Lamp

System

active

Lamp

System

active with

limitation

YES

OFF

System

active

YES

OFF

YES

OFF

Emergency

- EBD

YES

OFF

System

passive

NOTE :

For brake bleeding procedure conventional/ using

diagnostic tool refer Brakes group.