LR3/Disco 3
At speeds from >50 to 80 km/h (>31.3 to 50 mph) the HDC information indicator flashes and, on vehicles with the
high line instrument cluster, a message advising that the speed is too high is displayed in the message center. For
additional information, refer to
Instrument Cluster
(413-01 Instrument Cluster)
If the HDC switch is pressed while vehicle speed is more than 80 km/h (50 mph), the HDC information indicator
will not illuminate and HDC will not be selected.
If the speed reaches 80 km/h (50 mph) or more, a warning chime sounds, the HDC function is switched off, the
information indicator goes off and, on vehicles with the high line instrument cluster, a message advising that HDC
has been switched off is displayed in the message center.
When HDC is enabled, the ABS module calculates a target speed and compares this with the actual vehicle speed. The
ABS module then operates the HCU, in the active braking mode, as required to achieve and maintain the target speed.
During active braking for HDC, the ABS module also energizes the HDC relay to operate the stop lamps. Applying the foot
brakes during active braking may result in a pulse through the brake pedal, which is normal.
The target speed varies, between minimum and maximum values for each gear and transmission range, depending on
driver inputs through the foot pedals. If the foot pedals are not operated, the ABS module adopts a default target speed.
Low Range Target Speeds
High Range Target Speeds
The target speed is varied between the minimum and maximum values using the accelerator pedal.
The target speed can also be varied by pressing the speed control '+' and '-' buttons (where fitted). For additional
information, refer to
Speed Control
(310-03A Speed Control)
For additional information, refer to
Speed Control
(310-03B Speed Control - 2.7L Diesel)
During changes of target speed, the ABS module limits deceleration and acceleration to -0.5 m/s
2
(-1.65 ft/s
2
) and +0.5
m/s
2
(+1.65 ft/s
2
) respectively.
On manual transmission models target speed changes are suspended during gear changes, to prevent unwanted braking
when the accelerator pedal is released to change gear. The ABS module determines a gear change is occurring from:
Gear position information on the high speed CAN bus.
The rate of release of the accelerator pedal.
The status of the clutch pedal.
To provide a safe transition from active braking to brakes off, the ABS module invokes a fade out strategy, which
gradually discontinues the braking effort, if it detects any of the following during active braking:
Limit
Speed, km/h (mph)
Gear
Automatic Transmission Manual Transmission
1, R
D, 2 to 6
1, R
2 to 6
Default
3.5 (2.19)
6 (3.75)
3.5 (2.19)
6 (3.75)
Minimum
3.5 (2.19)
3.5 (2.19)
3.5 (2.19) 3.5 (2.19)
Maximum
20 (12.5)
20 (12.5)
20 (12.5)
20 (12.5)
Limit
Speed, km/h (mph)
Gear
Automatic Transmission Manual Transmission
1, R
D
1, R
Default
6 (3.75)
10 (6.25)
6 (3.75)
Minimum
6 (3.75)
6 (3.75)
6 (3.75)
Maximum
20 (12.5)
20 (12.5)
20 (12.5)
