Removing and installing emergency braking function sensor unit J939 — VW

Removing and installing
emergency braking function sensor unit
J939
General description
The emergency braking function detects the traffic situation by means of the
emergency braking function sensor unit
J939
attached to the interior mirror up to a distance of around 10 metres in front of the vehicle in a speed range of approximately 5 km/h to 30 km/h.
If the system detects a possible collision with a vehicle driving in front, the vehicle is prepared for possible emergency braking. If the driver does not react to the threat of a collision, the system can brake the vehicle automatically in order to reduce the speed for a possible collision. If the emergency braking function determines that the driver does not brake sufficiently when faced with the threat of a collision, the system can increase the braking force in order to reduce the speed for a possible collision.
In the following situations, it is possible that the emergency braking function will not react:
In tight curves
When accelerator pedal is fully depressed
If emergency braking function has been switched off or is faulty
If the laser sensor is dirty, is covered or has overheated
During a snowfall, in heavy rain or in dense fog
If vehicle is offset in relation to other vehicles
When other vehicles cut across the driving direction
When there are oncoming vehicles in the same lane
If vehicles are dirty with a low degree of reflection
When there is a lot of dust in the air
Note
When the emergency braking function triggers a braking process, the pedal travel of the brake pedal decreases. As a result, the brake pedal feels
“harder”
.
During automatic braking carried out by the emergency braking function, it is possible that unusual noises will occur. These are normal and are caused by the brake system.
Automatic braking triggered by the emergency braking function can be cancelled by depressing the clutch pedal or the accelerator pedal, or by turning the steering wheel.
Fault detection and fault display
The sensor unit for the emergency braking function has a self-diagnosis feature.
For fault finding
Vehicle diagnostic tester
use
“Guided fault finding”
mode.
The
sensor unit for the emergency braking function
J939
is located under a cover next to the interior mirror.
Removing
Switch off ignition and all electrical loads, and pull out ignition key.
Remove cover from interior mirror
General body repairs, interior
Rep. gr.
68
Interior mirror; Assembly overview - interior mirror
.
Disconnect connector
1
.
Pull catch
arrow
and remove
sensor unit for emergency braking function
J939
2
from holder on windscreen.
Installing
Install in the reverse order of removal, observing the following:
Note
Before installing, make sure that the sensor unit lenses and the windscreen in the installation area are clean in order to avoid malfunctions.
When installing the sensor unit
2
, first push it into the mounting
3
and then lock it securely into place with the catch
arrow
.
Note
If the
sensor unit for the emergency braking function
J939
is removed, installed or replaced, coding or adaptation is not necessary.