Scheme 10
Scheme 11
GENERAL
PDC provides an audible warning to the driver when any obstacles are in the path of the vehicle during a reversing maneuver. The purpose of the system is to assist the driver when parking or maneuvering in restricted space. It is not designed as a crash avoidance system or a replacement for visual interpretation for the driver.
The system comprises four ultrasonic sensors in the rear bumper, a control module, a fascia mounted control switch and a rear 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 deactivate the PDC system, if operation is not required.
PDC ECU
The PDC ECU is located in the rear right hand side of the luggage compartment, behind the side trim panel.
The PDC ECU uses a single microprocessor to perform the following tasks
- Control Of The Ultrasonic Sensors
- Monitoring Of The Sensors
- Evaluation Of Received Echo Signals From The Sensors
- Noise And Disturbance Suppression
- Control Of The PDC Sounder
- Monitoring Of The Sounder And Lead
- Control And Monitoring Of The Switch Status LED And Lead
- Evaluation And Monitoring Of The Control Inputs
- Management Of Diagnostic And Test Functions
- Monitoring Of Power Supply
- Communication Via Diagnostic Link
Scheme 12
The following tables give input/output information for the two harness connectors used on the PDC ECU.
| Pin No. | Description | InputOutput |
|---|---|---|
| 1 | Ignition switch power supply | Input |
| 2 | Sounder - Negative | Input |
| 3 | Not used | |
| 4 | PDC switch | Input |
| 5 | Not used | |
| 6 | Reverse gear signal | Input |
| 7, 8 and 9 | Not used | |
| 10 | Sounder - Positive 12V supply | Output |
| 11 and 12 | Not used | |
| 13 | PDC switch | Output |
| 14 and 15 | Not used | |
| 16 | Ground |
CONNECTOR C0958
| Pin No. | Description | InputOutput |
|---|---|---|
| 1 | Not used | |
| 2 | Sensor - RH Inner - Signal | Input |
| 3 | Sensor - LH Inner - Signal | Input |
| 4 | Sensor - RH Outer - Signal | Input |
| 5 | Sensor - 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 |
CONNECTOR C0957
INPUTS AND OUTPUTS
Two connectors provide the interface between the PDC ECU and the external PDC components.
The ECU receives inputs from the following
- Reverse lamp circuit - for system activation when reverse gear is selected
- PDC switch - fro activation and de-activation of the system
- Ignition switch - power supply for system operation.
The ECU outputs to the following
- Sensors - power and ground connections
- Sensors - digital signal transmit and receive signals
- Sounder - signal for sounder operation
- PDC switch - power supply for switch LED operation.
DIAGNOSTICS
The PDC ECU has no diagnostic connection to enable faults to be retrieved using T4 scan tool. 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.
Scheme 13
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.
In the combined mode, the sensor emits a series of ultrasonic impulses and then switches to receiver mode to receive the echo reflected by an obstacle in the detection range. These echo signals are amplified and converted from an analogue signal to a digital signal by the sensor. The digital signal is then transmitted to the PDC ECU and compared with preprogrammed data stored in an EEPROM within the ECU. The ECU receives this data via the signal line from the sensor and calculates the distance to the obstacle according to the elapsed time between the transmitted and received impulse. The duration of the impulse transmission is determined by the module. The sensor determines the frequency of the impulse.
In the receiver mode, the sensor will receive impulses that were emitted by adjacent sensors. The ECU uses this information to precisely determine position and distance of the obstacle.
PDC SWITCH
Up to 2004 model year the PDC switch is located in the rear of the centre console. From 2004 model year the PDC switch is located in the fascia outboard of the steering wheel.
Scheme 14
Scheme 15
The PDC 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 deactivated 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, which illuminates when the system is active. If a fault exists in the PDC system, the ECU flashes the LED continuously while reverse gear is selected.
Scheme 16
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 RH side of the rear 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. The sounder is connected to the PDC ECU via a harness connector.
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.
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 2000 mm (78.7 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 370 mm (14.5 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.
Scheme 17
Scheme 18
A = Intermittent Warning Tone; B = Continuous 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 recognizes the distance from the vehicle to the nearest object.