Range Rover P38
70
BRAKES
NEW RANGE ROVER
24
DESCRIPTION AND OPERATION
Diagnostics
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 TestBook to the vehicle diagnostic
connector in the passenger footwell, near the centre
console.
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 for current and
historic faults. The stored fault codes can be
accessed, read and then cleared when the fault is
rectified.
Driving the vehicle
WARNING: On surfaces which are soft and
deep, for example deep powdery snow,
sand or gravel, braking distance may be
greater than with non ABS braking. In these
conditions wheel lock and the build up of snow or
gravel under wheels may be an aid to shorter
stopping distance. However it is still an advantage
to maintain the stability and manoeuvrability
available with ABS control.
1. Switch on ignition, system will automatically
carry out self test function. This will be felt as a
slight movement in brake pedal and a short,
rapid series of clicks indicating that solenoid
valves have been checked.
2. 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.
Note time taken to pressurise system is up to 40
seconds.
3. Start vehicle and drive away, at 7 km/h (5 mph)
the ABS warning light must be extinguished.
See this section.
4. In road conditions where surface friction is
sufficient to slow or stop the vehicle without
wheel lock, ABS does not operate.
5. 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.
6. ABS operation will be felt as a vibration through
pedal, at same time solenoid cycling will be
heard.
NOTE: Constant pressure on foot pedal
whilst ABS is operating is more effective
than cadence braking. Do not pump brake
pedal, this may reduce ABS efficiency and
increase stopping distance.
7. Downward travel of pedal will also feel hard at
point at which ABS operates. Little further pedal
travel is possible at this point, BUT, force on the
pedal can be varied to influence braking force
while ABS retains control.
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 footwell mats.
8. 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 results in longer pedal
travel and greater pedal effort required to
decelerate 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.