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ANTI LOCK BRAKING SYSTEM (ABS)
15
ANTI-LOCK
BRAKING
SYSTEM (ABS)
C. ABS SYSTEM FAILURE WARNING LIGHT
Function
Warning Lamp
Cause of System failure
ABS
EBD
ABS
EBD
None
Operates
Operates
OFF
OFF
One Wheel Speed Sensor
Failure
does not operate
Operates
ON
OFF
Failure of more than 2
wheel speed sensors
does not operate
does not operate
ON
ON
Pump Failure
does not operate
does not operate
ON
ON
Battery voltage low
(V>8.4 and V < 10)
does not operate
Operates
ON
OFF
Battery voltage low
(V<8.4)
does not operate
does not operate
ON
ON
Battery voltage High
(V>17.5)
does not operate
does not operate
ON
ON
Valve failure
does not operate
does not operate
ON
ON
ECU Internal failures
does not operate
does not operate
ON
ON
In normal conditions when the ignition is switched on
the ABS and EBD lamp will come on and then switch
off after 1 - 2 seconds. During this period the system
will perform self diagnosis is to confirm that all inputs
and outputs are working correctly.
If the ABS warning lamp remains on after this time it
means either:
1. The ABS system has not been connected or the
connector is loose.
2. The system has detected a failure and will need
to be diagnosed.
3. Battery or Ignition line fuses have blown out.
4. Ignition line is cut.
The EBD lamp is shared with the brake fluid level
and parking brake, hence if the EBD warning lamp
remains on after this time it means either:
1. The park brake is applied
2. The Brake fluid level is low
3. The ABS system has not been connected. or the
connector is loose.
4. Park brake switch/ harness of parking brake or
brake fluid is loose
5. The system has detected a failure and will need
to be diagnosed.
If the warning light does not come on during Ignition,
the fault should be sought in the Instrument Cluster.
If the ABS system detects any fault that may
adversely affect its performance it will switch to a fail
safe shut down mode. When this happens the
electricity supply to the solenoid valves is
deactivated, stopping control signal output, this
causes the valves to switch to their default state.
(Open for inlet valves / Closed for Outlet valves)
In this condition, the conventional hydraulic brake
circuit will still function, allowing brake pressure to
reach all wheels. It should be noted that with an ABS
fault it will be possible to lock the wheels and in the
Case of an EBD failure the brake force proportioning
between front and rear will no longer function and
hence rear wheel lock is possible before front wheel
lock