sensor LAND ROVER DISCOVERY 1999 Workshop Manual

DRIVING AIDS
DESCRIPTION AND OPERATION 86-8-3
1PDC sounder
2PDC switch
3Fusible link
4Ignition switch
5Fuse
6PDC ECU
7PDC sensors

DRIVING AIDS
86-8-4 DESCRIPTION AND OPERATION
Description
General
Park Distance Control (PDC) is introduced on vehicles from 03 model year. PDC provides an audible warning to the
driver when any obstacles are in the path of the vehicle during a reversing manoeuvre. The purpose of the system is
to assist the driver when parking and is not designed as a crash avoidance system or a replacement for visual
interpretation by the driver.
The system comprises four ultrasonic sensors in the rear bumper, an ECU, a fascia mounted momentary switch and
a sounder unit. The system operates using ultrasonic signals which are transmitted by the sensors. The reflected echo
from this output is received by the sensors and used by the PDC ECU to calculate the distance from an object.
The fascia mounted switch allows the driver to de-activate the PDC system if operation is not required or the vehicle
has a trailer attached.

DRIVING AIDS
86-8-6 DESCRIPTION AND OPERATION
PDC ECU Connector Pin Details
aConnector C0958
bConnector C0957
Connector C0958
Connector C0957
Pin No. Description Input/Output
1 Ignition switch power supply Input
2 Sounder - Negative Input
3 Not used–
4PDC Switch Input
5 Not used–
6 Reverse Gear signal Input
7 Not used–
8Ground–
9 Not used–
10 Sounder - Positive 12V supply Output
11 Not used–
12 Not used–
13 PDC Switch LED Output
14 to 16 Not used–
Pin No. Description Input/Output
1 Not used–
2 Sensor - RH Inner - Signal Input
3 Sensor - Rear LH Inner - Signal Input
4 Sensor - Rear RH Outer - Signal Input
5 Sensor - Rear LH Outer - Signal Input
6 and 7 Not used–
8 Ground - All sensors Input
9 Not used–
10 Power Supply - All sensors Output
11 and 12 Not used–

DRIVING AIDS
DESCRIPTION AND OPERATION 86-8-7
Inputs and Outputs
Two connectors provide the interface between the PDC ECU and the external PDC components.
The ECU receives inputs from the following:
lReverse lamp circuit – for system activation when reverse gear is selected
lPDC switch – for activation and de-activation of the system
lIgnition switch – power supply for system operation.
The ECU outputs to the following:
lSensors – power and ground connections
lSensor – digital signal transmit and receive signals
lSounder – signal for sounder operation
lPDC Switch – power supply for switch LED operation.
Diagnostics
The PDC ECU has no diagnostic connection to enable faults to be retrieved using TestBook/T4. An on-board
diagnostic routine monitors the system and alerts the driver to a system fault by emitting a tone from the sounder.
If a PDC system fault has occurred, the sounder will emit a continuous tone for 3 seconds and the PDC switch LED
will flash continuously when reverse gear is selected.

DRIVING AIDS
86-8-8 DESCRIPTION AND OPERATION
Sensors
Four sensors are positioned in the rear bumper. Each sensor comprises an outer housing with an angled rubber trim
which differs between the inner and outer sensors and the sensor body. The outer housing has a slot which engages
with a pin on the sensor body and is locked by rotating the sensor. A coil spring around the sensor is compressed
when the sensor is installed in the bumper and maintains the sensor housing engaged on the pin. The sensor housing
has a raised lip at the top which locates in a corresponding groove in the bumper mounting hole and sets the correct
orientation for the sensor body.
Each sensor has a three pin connector which connects into a common harness linking all four sensors. This harness
is connected to the main vehicle body harness. The three pins are for sensor negative and positive feeds and a signal
line.
Each sensor comprises a plastic housing which contains a piezoelectric disc. The disc resonates at a frequency of
38.4kHz, producing an ultrasonic signal output. The disc also receives the reflected echo signal.
The PDC ECU controls the operating mode of each sensor by output of a digital signal on the signal line. Each sensor
has two modes of operation; combined transmitter and receiver mode or receiver mode only.

DRIVING AIDS
DESCRIPTION AND OPERATION 86-8-11
Operation
PDC System Operation
When the ignition switch is in position II and reverse gear is selected, the PDC sensors are automatically activated.
The PDC ECU only activates the system if reverse is selected for more than 1 second. This avoids nuisance audible
warnings when the gear selector lever is being moved between Drive and Park on vehicles with automatic
transmission.
When the system is activated, the PDC ECU illuminates the indicator LED in the PDC switch, switches on the
ultrasonic sensors and generates a single chime on the PDC sounder to indicate the system is active. If an object is
range of the sensors when the system is activated, a series of audible warnings are emitted by the PDC sounder
immediately.
If PDC operation is not required, it can be suspended temporarily by pressing the PDC switch. When reverse is
deselected and subsequently reselected, PDC will automatically become active again.
PDC can also be manually selected when not in reverse gear by pressing the PDC switch. A second press of the
switch is required to turn off the PDC or the PDC will be deactivated if reverse is selected and then deselected.
Sensor Operation
The PDC ECU processes the distance readings from the ultrasonic sensors to determine if there are any objects
within the detection areas. If there are no objects in the detection areas, there are no further audible warnings. If an
object is detected, repeated audible warnings are produced on the PDC sounder.
The maximum detection range is 1800 mm (70 in). When an object is detected, the time delay between the audible
warning tones decreases as the distance between the detected object and the vehicle decreases until, at
approximately 450 mm (17 in), the audible warning tone is continuous.
After the initial detection of an object, if there is no decrease in the distance between an object and the central sensors,
the time delay between the audible warnings remains constant. If an object is detected by one of the corner sensors
only, the audible warnings stop after about 5 seconds if there is no change in the distance between the object and the
corner sensor.

DRIVING AIDS
86-8-12 DESCRIPTION AND OPERATION
Park Distance Control Detection Areas
aIntermittent Warning Tone
bContinuous Warning Tone
Detection Calculation
When operating in the combined transmitter and receiver mode, the sensor outputs a number ultrasonic pulses and
receives the reflected echo signal. The ECU amplifies the received echo signals and compares them with a
preprogrammed threshold to calculate the distance to the object. This is achieved by determining the elapsed time
between the transmission and reception of the ultrasonic signal.
When operating in receiver mode, the sensor receives echo signals transmitted by an adjacent sensor. This mode is
used to improve the accuracy of the system.
The detection cycle consists of the ECU operating one sensor in the combined transmitter and receiver mode and
transmitting a number of ultrasonic pulses. The ECU then switches the transmitting sensor and the adjacent sensor(s)
to receiver mode. After a short time delay, this sequence is repeated using a different sensor to transmit the ultrasonic
pulse and continues until all four sensors have output an ultrasonic signal. This sequence is completed in 100ms. The
ECU uses several measurements of the same sensors to remove errors from the calculation.
If the object is directly behind a sensor, the distance is calculated using the time between the transmission and
reception of the signal. If the object is positioned between two sensors, the ECU uses both signals to determine the
correct distance using triangulation.
To perform the triangulation calculation, the ECU must know the distance between the individual sensors in the
bumper. This information is stored in the ECU memory. From the received distance from each sensor and using the
known distance between adjacent sensors, the ECU can calculate the minimum distance from the vehicle to the
object.
When approaching several objects, the ECU recognises the distance from the vehicle to the nearest object.
A
Y- Y
1800mm (70in)
450mm (17in)
600mm (23.5in)
YY
B
M86 5917

DRIVING AIDS
REPAIRS 86-8-15
Sensor - parking aid - rear - inner
$% 86.54.23
Remove
1.Remove rear bumper assembly.

+ EXTERIOR FITTINGS, REPAIRS,
Bumper assembly - rear - from 03MY.
2.Remove 7 bolts and 5 screws securing closing
panel and remove panel.
3.Disconnect multiplug from sensor.
4.Release and remove sensor and sensor
housing.Refit
1.Clean sensor location on bumper.
2.Fit sensor housing to bumper, ensuring lug on
housing is aligned with cut-out in bumper.
3.Fit and secure sensor to housing.
4.Connect multiplug.
5.Fit closing panel and secure with bolts and
screws.
6.Fit bumper assembly.

+ EXTERIOR FITTINGS, REPAIRS,
Bumper assembly - rear - from 03MY.

DRIVING AIDS
86-8-16 REPAIRS
Sensor - parking aid - rear - outer
$% 86.54.24
Remove
1.Remove tail lamp from bumper.

+ LIGHTING, REPAIRS, Lamp - tail/
flasher - bumper.
2.Disconnect multiplug from sensor.
3.Release and remove sensor and sensor
housing.
Refit
1.Clean sensor location on bumper.
2.Fit sensor housing to bumper, ensuring lug on
housing is aligned with cut-out in bumper.
3.Fit and secure sensor to housing.
4.Connect multiplug.
5.Fit tail lamp.

+ LIGHTING, REPAIRS, Lamp - tail/
flasher - bumper.

NAVIGATION SYSTEM
87-2 DESCRIPTION AND OPERATION
Description
General
The navigation system provides audio and visual route guidance to help the driver reach a selected destination. The
system is an optional fit consisting of a Traffic Pro navigation computer and antenna, manufactured by Harman/
Becker Automotive Systems, which are fitted in place of the In Car Entertainment (ICE) head unit and antenna.
Compact Disc (CD) and radio functions are incorporated into the navigation computer.
The navigation system allows the driver to choose between the shortest and fastest routes between the vehicle's
current position and a selected destination, and to select a stopover point in the journey and a route that avoids
motorways, ferries and toll roads. Directions to Points Of Interest (POI) e.g. airports, hospitals, petrol stations etc,
either local, national or in another country, can also be selected. A traffic jam function enables the driver to request
diversion instructions, around an obstructed part of the selected route, during the journey. A Traffic Management
Control (TMC) function, currently only available in some European countries, monitors traffic broadcasts and
automatically selects an alternative route during the journey if the original route is effected by a traffic jam, accident
or road works etc.
The position of the vehicle is determined by the navigation computer using a combination of vehicle sensor inputs and
radio signals from the 24 Global Positioning System (GPS) satellites orbiting the earth. The position of the vehicle is
then plotted on a digitised map, loaded into the navigation computer from a CD-ROM, to determine the journey route
and provide the route guidance.
The GPS satellite signals are used for initial determination of the vehicle's position and periodic position updates. The
vehicle sensor inputs are used to monitor the vehicle's direction of travel and distance travelled between position
updates from the GPS satellite signals. The vehicle sensor inputs consist of:
lA vehicle speed signal from the ABS ECU, to monitor the distance travelled and for automatic volume control.
lA reverse gear signal from the selector and inhibitor switch of the automatic gearbox, or reverse gear switch of
the manual gearbox, to enable the navigation computer to differentiate between forward and rearward movement
of the vehicle.
lA gyro in the navigation computer, to monitor changes of direction, i.e. steering inputs.
The signal from each GPS satellite contains information about satellite position, almanac data and time (almanac data
is the current status of the satellite). Signals from between five and 11 of the GPS satellites can be received at a given
point on the earth's surface at any one time. The number and quality of separate GPS satellite signals received also
varies with vehicle location. In hilly or tree lined areas, built up areas with tall buildings, multi-storey car parks,
garages, tunnels, bridges and during heavy rain/thunderstorms, signal reception of some or all of the GPS satellites
will be poor or non existent.
A minimum of three separate GPS satellite signals are required for the navigation computer to calculate a three
dimensional (3D) positional fix. When only two signals are being received, the navigation computer will calculate a
less accurate two dimensional (2D) positional fix. The more widely dispersed that the GPS satellites are, the more
accurate the positional fix. The navigation computer can store information from a maximum of 12 GPS satellites at
any one time. When more than three signals are stored, the navigation computer selects the three most widely
dispersed signals for the position calculation.
GPS Antenna and diplexer unit
The GPS antenna is installed at the rear of the roof on the centreline. A diplexer unit on the underside of the GPS
antenna amplifies the radio signals received from the GPS satellites and transmits them through separate dedicated
co-axial cable to the navigation computer for processing.