RT-3 USER GUIDE____________________________________________________
9.2.1 INTRODUCTION
The market’s present requirements have promoted the introduction of electronic
systems to avoid or difficult the vehicles´ robbery. These systems protect from igniting the
vehicle by unauthorized people by means of a key recognition electronic system and codified
ECUs.
NISSAN uses a kind of immobilizer system named NATS.
9.2.2 OPERATION
There is a dialog through an interconnection channel between the injection ECU and the
immobilizer ECU, to allow or not the vehicles´ ignition. This protection is implemented at
two levels; so, there are two conditions to be fulfilled for the athorization to take place:
1.
The immobilizer´s ECU is programmed to allow the starting only with the previously
right coded injection ECU. This means that in case of replacement of one of the
ECU’s, the immobilizer must be programmed to recognise the new engine ECU.
2.
The immobilizer authorizes to start only if the key’s code has already been stored by
the system ECU. That means that in case the customer needed a new key, this should
be recognized and memorized by the immobilizer.
The
steps
done
by the
ECU before authorizing the ignition are the following:
The user enters the key and turns it on. Each key has a chip that emits a code when
excited by a radio-frequency signal. That signal is emitted from the ignition lock
cylinder when the contact has been done, then, a sensor reads the key’s emitted code.
The immobilizer ECU compares the read code with the stored codes(with a maximum
of four).If the read code matches with one of the stored codes, the immobilizer ECU
authorizes the starting. On the contrary, if the user tries to start the vehicle, the engine
won’t even try to rotate putting the immobilizer´s light on.
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