Discovery 2. Manual — part 354

DRIVING AIDS

DESCRIPTION AND OPERATION

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Inputs and Outputs
Two connectors provide the interface between the PDC ECU and the external PDC components.

The ECU receives inputs from the following:

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Reverse lamp circuit – for system activation when reverse gear is selected

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PDC switch – for activation and de-activation of the system

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Ignition switch – power supply for system operation.

The ECU outputs to the following:

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Sensors – power and ground connections

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Sensor – digital signal transmit and receive signals

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Sounder – signal for sounder operation

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PDC 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.

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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

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PDC Switch

The PDC switch is located in the instrument pack cowl, below the fuel flap release switch. The switch has a
momentary, non-latching action, which switches a positive output from the PDC ECU to ground when pressed. This
signal is used by the ECU to switch the PDC between the activated and de-activated conditions. The switch is
connected to the PDC ECU via a harness connector which is integrated into the vehicle body harness.

The switch contains an LED. The LED illuminates for approximately 3 seconds when the ignition is switched to
position II for a bulb check. The bulb check is controlled by logic within the PDC ECU. When the system is active (i.e.
obstacle detected), the LED illuminates to show the active condition.

When the PDC is switched from the off condition to the active condition, the LED is illuminated briefly, along with a
chime from the sounder, to signal that the system has been activated.

If a fault exists in the PDC system, the ECU flashes the LED continuously, when the switch is pressed to activate the
system.

DRIVING AIDS

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Sounder

The PDC sounder is controlled by the PDC ECU and emits a series of tones of varying frequency to inform the driver
of the distance between the vehicle and a detected object.

The PDC sounder is located in the LH side of the luggage compartment. A bracket is attached to the 'E' post, behind
the trim panel and provides for the attachment of the PDC sounder and the PDC ECU.

On vehicles without rear air conditioning, the bracket is located inboard on the LH 'E' post, adjacent to the luggage
compartment trim panel. On vehicles with rear air conditioning, the bracket is located outboard on the LH 'E' post,
adjacent to the outer body panel.

The sounder is located on two screws and lock washers through the bracket and secured with nuts. The sounder is
connected to the PDC ECU via a harness connector.