I thought so as well, however here's what I located from Rover:
This addresses the P1663 and P1664 Faults, but local Rover shop says not related to Three Amigos and that P1663 and P1664 are Engine codes???
4.26 Hill Descent Control Signal ñ Discovery Series II Only
HDC operates in conjunction with the anti-lock braking system to provide greater control in off-road situations if necessary. HDC can be selected with
the vehicle in any gear, but will only operate when low range gears are engaged with the vehicle traveling at less than 31 mph. During a descent, if
engine braking is insufficient to control the vehicle speed, HDC (if selected) automatically operates the brakes to slow the vehicle and maintain a
speed relative to the selected gear and the accelerator pedal position.
The ECM transmits throttle angle, engine torque, engine identification (V8 Thor) and transmission type to the SLABS control module to support the
HDC system. This information is transmitted via a multiplexed PWM waveform.
The ECM has power stage diagnostics for the signal, with a fault being detected if any of the following conditions is satisfied: -
1. HDC link to the SLABS control module short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the
driver is on.
2. HDC link to the SLABS control module short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the
driver is off.
3. HDC link to the SLABS control module open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two
thirds of the battery voltage when the driver is off.
Hill Decent Control Signal
Hill Decent P1665 circuit continuity - voltage - drive on voltage > 1/2 * Battery positive engine speed > 80 rpm immediately/ two driving
Control short to battery positive battery voltage 7.5V < Battery positive < 17V continuous cycles
Signal P1664 circuit continuity ñ short to ground voltage - drive off voltage < 1/3 * Battery positive
P1663 circuit continuity ñ open circuit voltage - drive off 1/3 * Battery positive < voltage < 2/3 * Battery positive
If the above table does not include details of the following enabling conditions: - IAT, ECT, vehicle speed range, and time after engine start-up then
the state of these parameters has no influence upon the execution of the monitor.
Land Rover Revision Date: December 2003 Page 93 of 98
4.27 Engine Speed