Useful information about the “behaviour of the control unit in the event of a gearbox fault” — VW

Useful information about the
“behaviour of the control unit in the event of a gearbox fault”
The control unit works with highly developed software. This software is able to execute, monitor and control electronic functions in milliseconds. This control unit
»has everything«
that a modern gearbox electronics
»has to offer«
. Consider this as well when searching for faults.
But no electronics system can do something that it was not designed for. So it is just not possible to identify electronically, for example, where oil is leaking from the gearbox housing. But it is possible to detect the effects of
»insufficient oil«
. First a fault in
“gear monitoring”
will be detected and finally the control unit will react by opening both clutches (no power transfer).
You should be aware of this when looking for faults and working with testers. It might happen that the source of a fault is not discovered with
Guided fault finding
.
In addition to the software which enables the operation of the gearbox at all, a great deal has been done to protect the gearbox in the event of a disturbance (security functions). Consequently, when a fault occurs, if it is necessary, the fault is saved and a substitute program is started.
Behaviour of the control unit in the event of a fault
If a component in the gearbox malfunctions, the control unit responds with a substitute function. Because the gearbox must be protected, there are 4 fault responses:
The fault is so minor that travel may be continued with a substitute program and driving safety will be preserved. The driver will not be warned via the
selector lever position display
Y5
. The display indicates the selector lever position as usual. It may be possible to notice changes in driving behaviour.
Individual selector lever positions blink in the
selector lever position display
Y5
. The driver is being warned that it is not possible to select this gear at the moment. For example, driving in reverse: the lever is in
“R”
and the vehicle is travelling backwards. If
“D”
is selected in this situation, the letter
“D”
in
selector lever position display
Y5
will begin blinking. In this situation, the control unit prevents 1st gear from being engaged to prevent damage to the gearbox. The gear will not be engaged until the vehicle has stopped moving. If you should want to try this out, be careful.
The
selector lever position display
Y5
is completely illuminated and is blinking. The selected selector lever position is recognisable or is highlighted. For example: the gearbox oil temperature is too high. Some possible causes may be the towing of a trailer with too great a load or retrofitted components at the front of the vehicle leading to
»insufficient air cooling«
.
The selected selector lever position is not recognisable. The
selected range display
Y5
flashes. Changes in driving and gearshift behaviour are clearly apparent. Reversing is not possible. A
»major fault«
has occurred. Part of the gearbox has been switched off and the gearbox must be repaired.