Parking System, Function - GF54.65-P-0006KJ
MODEL 453.0/3/4 with CODE 220 (Rear parking assist)
Function requirements, general
- Engine ON (except model 453.091/391/491)
- Drivetrain operational (vehicle in "READY" mode) (only model 453.091/391/491)
The parking system control unit controls the entire function of the rear parking assist. All the necessary electrical components are connected directly to the control unit.
Parking system, general
The parking system offered is a rear parking assist based on the ultrasonic measuring method. While reversing at speeds of v ≤ 10 km/h, obstacles behind the vehicle are detected and an acoustic warning is output.
The parking system function includes the following subfunctions:
- Measuring procedure function sequence
- Self-test function sequence
- Activate and deactivate function sequence
- Function sequence for monitoring of reverse travel
- Function sequence for diagnostic mode
Illustration of the principle of ultrasonic measurement
Measuring procedure function sequence
The rear parking assist is based on ultrasonic measurement. As such, the parking system control unit actuates the distance sensors directly. These then emit ultrasonic waves.
The ultrasonic waves reflected by an obstacle are received again by the distance sensors. The parking system control unit directly reads in the signals of the distance sensors and evaluates them. In principle a distinction is made between two measurements. On the one hand the direct measurement resulting from a direct echo and on the other hand the indirect distance measurement which is achieved via a cross echo (illustration of the principle). Echoes can usually also be received from adjacent distance sensors due to the large distance sensor detection angles; these are known as cross echoes. These occur at the obstacle due to scattered reflection. With the help of the triangulation method, the distance from the sensor, and thus from the vehicle, to an obstacle can be calculated from two echo signals. The propagation times of the signals from the direct measurement and from the indirect measurement (cross echo) are required for this method. A long signal propagation time corresponds to a large distance, and a short signal propagation time corresponds to a short distance to the obstacle.
The parking system may not work correctly in some cases because of the functional principal (sending and receiving of ultrasound waves). For example, when approaching a strong sound-deadening obstacle (e.g. a vehicle covered in snow) it is possible that false data may be calculated.
Self-test function sequence
During the self-test the following components are checked for proper operation:
- Distance sensors
- Parking system warning buzzer
- Parking system control unit
The self-test does not check the input signals of reverse gear and of the parking system switch.
The parking system control unit performs the self-test when the ignition is switched on. Also, a self-test is performed every time reverse gear is engaged.
If the parking system control unit detects a fault during the self-test, the parking system changes to failure mode. In failure mode, the status LED in the parking system switch is activated continuously and the parking system is deactivated. If reverse gear is engaged in failure mode, the parking system warning buzzer emits a fault warning for a duration of t = 3 s.
When the parking system is in failure mode, the acoustic fault warning can be switched on and off by pressing the parking system switch.
If the parking system switch is held down for at least 3 seconds in failure mode, the parking system control unit switches to diagnostic mode.
Additional function requirements for activation and deactivation
- Self-test completed successfully
- Drive position "R" engaged
Activate and deactivate function sequence
The rear parking assist can be permanently deactivated or activated by pressing the parking system switch. This selection is saved even after the engine is switched off.
If the indicator lamp in the parking system switch is on, the parking assist is not active.
If the indicator lamp in the parking system switch is off, the parking assist is active.
When the parking assist is defined as active by the parking system switch, parking assistance is automatically activated by engaging reverse gear with the engine running.
When reverse gear is engaged, an acoustic signal is emitted for 0.5 s to indicate that the parking assist system is ready.
The parking assist switches itself off automatically
- When a speed of v = 10 km/h is exceeded
- When reverse gear is no longer engaged
Shows on model 453.3
Additional function requirements for monitoring of reverse travel
- Vehicle speed v < 10 km/h
- Drive position "R" engaged
Function sequence for monitoring of reverse travel
When the vehicle is reversing, the area behind the vehicle is monitored by the distance sensors. If these detect an obstacle, this information is sent directly to the parking system control unit. This evaluates the information and sends a signal directly to the warning buzzer according to the distance of the obstacle from the vehicle. If several obstacles are detected, the parking system warning buzzer indicates the obstacle closest to the vehicle.
| Distance to obstacle | Repetition frequency | Frequency of parking system warning buzzer |
|---|---|---|
| Less than 0.4 m | Continuous | Continuous |
| Between 0.4 m and 0.7 m | High | 8 Hz |
| Between 0.7 m and 1.2 m | Low | 4 Hz |
The parking assist does not detect obstacles located above or below the detection zone, e.g.:
- Animals
- Objects
- Overhanging cargo
- Overhangs or loading ramps
LB The sensors must be free of dirt, ice and slush.
Function sequence for diagnostic mode
When the parking system control unit is in failure mode, diagnostic mode can be called up by holding down the parking system switch for 3 seconds.
To confirm that diagnostic mode is active, the indicator lamp in the parking system switch flashes three times for t = 0.5 s at a frequency of f = 1 Hz. This indication is accompanied by a continuous acoustic warning of t = 3 s from the parking system warning buzzer, unless the parking system warning buzzer is defective. In this case, successful activation of diagnostic mode is indicated only by the flashing of the indicator lamp. After flashing three times and the 3-second continuous acoustic warning, the indicator lamp goes out for t = 0.6 s.
Subsequently, the fault identified by the parking system control unit in the self-test is displayed individually.
If the parking system control unit itself is identified in the self-test as the source of the fault, the parking system warning buzzer emits an acoustic warning of duration t = 6.4 s. The indicator lamp in the parking system switch remains permanently on.
If the parking system warning buzzer is identified in the self-test as the source of the fault, this is then indicated by five flashes of the indicator lamp in the parking system switch of t = 5 s each at a frequency of f = 0.5 Hz.
If one or more of the distance sensors is identified in the self-test as the source of the fault, the indicator lamp lights up once for each sensor identified as faulty, accompanied in each case by an acoustic warning with a duration of t = 1 s. The flashing and acoustic warning occur at different times depending on which sensor has been identified as faulty. If the left distance sensor is defective, the indication occurs immediately after the aforementioned 0.6-second pause. The indication for the center distance sensor follows after the time window of the left distance sensor, and the indication for the right distance sensor after the time window of the center sensor.
| Electrical function schematic of parking system | PE54.65-P-2054-97BBA | ||
| Overview of system components of parking assistance systems | GF54.00-P-9997KJ |