Chevrolet Trax Owner's Manual page 225

The system consists of four
ultrasonic parking sensors in the rear
bumper.
Note
The attached parts in the detection
area cause system malfunction.
Activation
When reverse gear is engaged, the
system is activated automatically. An
obstacle is indicated by audio.
The interval between the audios
becomes shorter as the vehicle gets
closer to the obstacle. When the
distance is less than 40 cm, the
audio sounds continue.
{Warning
Under certain circumstances,
various reflective surfaces on
objects or clothing as well as
external noise sources may cause
the system to fail to detect
obstacles.
Deactivation
Deactivated in drive, Park or if there
is an error.
The system might not detect the
obstacle when the vehicle is driven
above a 10km/h.
Fault
In the event of a fault in the system,
X illuminates.
Additionally if the system does not
work due to temporary conditions like
snow covered sensors, X
illuminates.
Driving and operating 223
Caution
The parking assistance system
should only be considered as a
supplementary function. The driver
must check the rearview.
The audio sounds can be different
depending on the objects.
The audio sounds might not
activate in case the sensor is
frozen or stained with dirt or mud.
Do not push, or scratch the surface
of the sensor. This will likely
damage the covering.
There is a chance of malfunction of
the parking assistance system
when driving on uneven surfaces
such as woods, gravel road,
jagged road, and slope.
The parking assistance system
might not recognise sharp objects,
thick winter clothes or other thick
and soft materials could be absorb
the frequency.