BRAKES
Minimum target speed
The minimum target speed depends on which gear is engaged. Reduced minimum target speeds are employed for
some gears if rough terrain or sharp bends are encountered while already travelling at the normal minimum target
speed. If loss of traction makes it impossible to maintain the minimum target speed, the SLABS ECU temporarily
increases the minimum target speed to maintain stability, then restores the normal minimum target speed when
traction improves.
HDC minimum target speeds
Gear
Speed, mph (km/h)
Manual gearbox
Automatic gearbox
Normal
4.4 (7.0)
5.2 (8.3)
6.0 (9.6)
7.5 (12.0)
8.8 (14.0)
3.5 (5.6)
8.8 (14.0)
Reduced
Normal
4.4 (7.0)
4.4 (7.0)
7.5 (12.0)
7.5 (12.0)
-
Reduced
1
4.4 (7.0)
4.4 (7.0)
4.4 (7.0)
6.0 (9.6)
7.0 (11.2)
3.5 (5.6)
4.4 (7.0)
4.4 (7.0)
6.0 (9.6)
6.0 (9.6)
-
2
3
4
5
Reverse
3.5 (5.6)
4.4 (7.0)
3.5 (5.6)
4.4 (7.0)
Neutral or clutch
disengaged
Last off road speed
Fade out
To provide a safe transition from active braking to brakes off, the SLABS ECU invokes a fade out strategy if it detects
any of the following during active braking:
l
l
l
A system fault.
The conditions for HDC are no longer being met.
Possible brake overheat.
The fade out strategy increases the target speed at a low constant acceleration rate, independent of actual throttle
position. This results in the braking effort being gradually reduced and then discontinued. The SLABS ECU operates
warning indications during fade out that are dependent on the cause.
Fade out warning indications
Cause
Warning indication
HDC fault warning lamp
HDC information
warning lamp
Audible warning
Fault detected
On
Off
Flashes
Flashes
Off
Continuous
Continuous
Continuous
HDC conditions not met
Brake overheat prevention
Flashes
Clutch disengagement/neutral selection
During active braking, if the SLABS ECU detects the clutch is disengaged or neutral is selected, it flashes the HDC
information warning lamp and sounds the audible warning continuously to indicate that conditions for HDC are no
longer being met. Initially, the SLABS ECU also fixes the target speed to the applicable minimum target speed, but if
the condition continues for approximately 60 seconds the SLABS ECU invokes fade out.
Brake overheat prevention
To prevent the brakes overheating, the SLABS ECU monitors the amount of active braking employed and, from this,
estimates brake temperature. If the SLABS ECU estimates the brake temperature has exceeded a preset limit, it
flashes the HDC fault warning lamp and sounds the audible warning continuously, to indicate that HDC should be
deselected to allow the brakes to cool. If active braking continues and the SLABS ECU estimates that brake
temperature has increased to an unacceptable level, fade out is employed and HDC is disabled. After fade out, the
audible warning is discontinued but the HDC fault warning lamp continues to flash, while HDC is selected, until the
SLABS ECU estimates brake temperature to be at an acceptable level. This calculation continues even if the ignition
is turned off, so turning the ignition off and back on will not reduce the disabled time. When the SLABS ECU estimates
the brake temperature to be acceptable, it extinguishes the HDC fault warning lamp and illuminates the HDC
information warning lamp to indicate that HDC is re-enabled. The disabled time is dependent on vehicle speed; typical
times at constant vehicle speeds are as follows:
70-22
DESCRIPTION AND OPERATION
| Categories | Land Rover Defender, Land Rover Discovery II, Range Rover |
|---|---|
| Tags | Land Rover |
| Model Year | 1999 |
| Download File |
|
| Document Type | Workshop Manual |
| Language | English |
| Product Name | Discovery Series II |
| Product Brand | Land Rover |
| Document File Type | |
| Publisher | landrover.com |
| Wikipedia's Page | http://en.wikipedia.org/wiki/Land_Rover |
| Copyright | Attribution Non-commercial |
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