LR3/Disco 3
HDC selected off with the HDC switch.
Failure of a component used by HDC, but not critical to fade out function.
Accelerator pedal pressed when transmission is in neutral.
Brake overheat.
If fade out is invoked because of deselection or component failure, the HDC function is cancelled by the ABS module. If
fade out is invoked because the accelerator pedal is pressed with the transmission in neutral, or because of brake
overheat, the HDC function remains in standby and resumes operation when the accelerator pedal is released or the
brakes have cooled.
The fade out strategy increases the target speed, at a constant acceleration rate of 0.5 m/s
2
(1.65 ft/s
2
), until the
maximum target speed is reached or until no active braking is required for 0.5 s. If the accelerator pedal is positioned
within the range that influences target speed, the acceleration rate is increased to 1.0 m/s
2
(3.3 ft/s
2
).
When fade out is invoked because of component failure, a warning chime sounds and the HDC information indicator is
extinguished. The HDC warning indicator is illuminated (low line instrument cluster) or a message advising there is a fault
is displayed in the message center (high line instrument cluster).
When fade out is invoked because of brake overheat on vehicles with the high line instrument cluster, a message
advising that HDC is temporarily unavailable is displayed. On vehicles with the low line instrument cluster, the HDC
warning indicator flashes. At the end of fade out, the HDC information indicator flashes. The flashing indicators and/or
message continue while HDC remains selected until the brakes have cooled.
To monitor for brake overheat, the ABS module monitors the amount of braking activity and, from this, estimates the
temperature of each brake. If the estimated temperature of any brake exceeds a preset limit, the ABS module invokes the
fade out strategy. After the fade out cycle, the HDC function is re-enabled when the ABS module estimates that all of the
brake temperatures are at less than 64% of the temperature limit.
ANTI-LOCK CONTROL DIAGRAM
NOTE :
A = Hardwired connections; D = High speed CAN bus
