TIAGO

BRAKES

6.14 TROUBLE

SHOOTING

DIAGNOSIS

General information:

While the ignition is in position II, the ABS ECU

monitors the system for faults. Diagnostic

information and system function monitoring can

be accessed by connecting diagnostic software

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 be

remain available. Fault codes are stored in the

ECU’s memory which can be accessed, read and

then cleared when the fault is rectified.

(a) During driving the vehicle with ABS operative:

1. Observe warning lights, check parking

brake/fluid warning light extinguishes after

initial bulb check or when parking brake is

released, indicating that power assistance is

available.

2. In road conditions where surface friction is

sufficient to slow or stop the vehicle without

wheel lock, ABS does not operate.

3. 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.

(b) Brake application with partial failure:

Warning:

If a fault develops in the brake system it is

essential that it is investigated immediately.

NOTE:

If, during braking, a drastically reduced

resistance is detected at pedal and braking

effectiveness is very much reduced, failure of

the non-powered (master cylinder) portion of

system is indicated. When this occurs, DO

NOT PUMP BRAKE PEDAL. Push the pedal

through free movement to obtain braking

effort from the power circuit. It is essential

that brake pedal travel is not obstructed by

items such as extra floor mats.

1. When power assistance is not available, ABS

braking is not operative. Both warning lights

are illuminated. Braking effort is available

from master cylinder only. This result in

longer pedal travel and greater pedal effort

required to decelerate vehicle.

NOTE:

Foot pressure on the pedal, using master

cylinder only, will not achieve the same

degree of braking as is

available

from

power

assistance.

2. If master cylinder fails, i.e. 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 indica-tor lamp) will be illuminated if

cause of the master cylinder failure is a fluid

leak and level in fluid reservoir is low enough

to actuate fluid level switch.

Warning:

Longer pedal travel is required, but power

assisted braking is available at reduced

efficiency.

NOTE:

The hydraulic connections to the hydraulic

modulator can be crossed over; the ECU self-

diagnosis will not detect it as a fault; nor will

it cause the system to be shut down or cause

a fault code to be logged in the ECU. When

the hydraulic modulator is exchanged or

repaired, the brake pipes to the solenoids

must be tested for correct assignment using

a diagnostics tester. When the inlet and

outlet valve are activated, e.g. on the front

left wheel, this must generate the necessary

changes at the wheel. If this does not

happen, the pipes have been crossed over.

This will cause the system to function

incorrectly.