69
The engine control unit has a set of equations.
It is also stored in the immobiliser control unit,
according to which the variable code is con-
verted into a secret code. The “Adapt immobi-
liser” function also saves in the control units
the result of key interrogation, the immobiliser
PIN, the immobiliser control unit ID as well as
the VIN . If all these data match up with one
another, vehicle start-up is enabled.
Due to the fact that a new variable code is
generated every time in this secret computing
processes, this code is not decipherable. It is
not possible to copy the vehicle key.
Functional description
After turning on the ignition, the key transpon-
der sends the fixed code to the immobiliser
control unit. If this is identified as correct, a
variable code is generated in the immobiliser
control unit. This code is sent to the transpon-
der.
A secret arithmetic process is started in the
transponder and in the control unit according
to a set of equations. The result of the compu-
ting process is evaluated in the control unit.
If the results tally, the vehicle key is acknow-
ledged as correct. The engine control unit then
sends a variable code to the immobiliser con-
trol unit.
Self-diagnosis
The immobiliser has extensive self-diagnosis
capability.
Address word:
17
You can find further information on the self-
diagnosis in the Workshop Manual “Electrical
System”.
Emergency start function
The emergency start function makes it possi-
ble to re-enable a vehicle which is stranded
because the immobiliser has been disabled.
The prerequisite for this is a knowledge of the
secret number. You can find further informa-
tion on the emergency start function in the
Workshop Manual “Electrical System”.
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Q
V.A.G - EIGENDIAGNOSE
HELP
17 - Schalttafeleinsatz
HELP
V.A.G 1551
SSP207/93
