Detection Calculation
In the combined mode, the sensors emit a series of ultrasonic impulses and then switch to receiver mode to receive the echo reflected by an obstacle within the detection range. The received echo signals are amplified and converted from an analogue signal to a digital signal by the sensor. The digital signal is passed to the Parking Aid Control Module (PACM) and compared with pre-programmed data stored in an electrically erasable programmable read only memory within the PACM. The PACM receives this data via the signal line from the sensor and calculates the distance from the object using the elapsed time between the transmitted and received impulse. The duration of the impulse duration is determined by the module, with the sensor controlling the frequency of the impulse output.
When in Reverse (R) gear, both the front and rear sensors are active, when in a forward gear, only the front sensors are active.
In receiver mode, the sensor receives impulses that were emitted by adjacent sensors. The PACM uses this information to precisely determine the position and distance of the object.
If no objects are detected there are no further warning tones. If an object is detected, repeated audible tones are emitted from either the front or rear audio speakers as appropriate. The time delay between the tones decreases as the distance between the object and the vehicle decreases, until at approximately 300 mm (12 inches), the audible tone becomes 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 approximately three seconds if there is no change in the distance between an object and the corner sensor.
When approaching several objects within detection range, the PACM recognizes the distance from the vehicle to the nearest object.
If it is in reverse gear only the object in the rear will be reported. If it is in drive only the object in the front will be reported. If two objects are detected at equal distance (one front one rear) the audible tones will alternate between the front and rear audio speakers.
If two objects are detected at equal distance (one front one rear) the audible tones will alternate between the front and rear audio speakers.
The volume output of the parking aid audible tones can be adjusted using the audio volume control when the parking aid system is activated. The volume can also be adjusted from the home menu screen by selecting 'Setup', 'System' followed by 'Volume Presets' on the Touch Screen (TS). The volume can be adjusted using the + or - selections on the TS.
The PACM receives a signal on the High Speed (HS) Controller Area Network (CAN) chassis systems bus from the Body Control Module/Gateway Module (BCM/GWM) assembly, when a trailer is equipped. When this signal is detected, the PACM suspends operation of the rear parking aid system. The ignition needs to be cycled once the trailer has been disconnected to activate the rear parking aid system.