Nissan Versa
Sedan Service Manual
Body exterior, doors, roof & vehicle security » Security control system (SEC)
Nissan anti-theft system

NISSAN ANTI-THEFT SYSTEM : System Description

SYSTEM DIAGRAM

SYSTEM DESCRIPTION

The Nissan Anti-Theft System (NATS) prevents the engine from being started by Intelligent Key whose ID is not registered to the vehicle (BCM). It has higher protection against auto theft involving the duplication of mechanical keys.
The ignition key integrated in the Intelligent Key cannot start the engine. When the Intelligent Key battery is discharged, the NATS ID verification is performed between the transponder integrated with Intelligent Key and BCM via NATS antenna amp. when the Intelligent Key backside is contacted to push-button ignition switch while brake pedal is depressed. If the verification result is OK, the engine start operation can be performed by the push-button ignition switch operation.
Locate the security indicator lamp and always blinks it when the ignition switch is in any position except ON to warn that the vehicle is equipped with Nissan Anti-Theft System (NATS).
Up to 4 Intelligent Keys can be registered (including the standard ignition key) upon request from the owner.
When replacing ECM, BCM or Intelligent Key, the specified procedure (Initialization and registration) using CONSULT is required.
Possible symptom of NATS malfunction is "Engine can not start". This symptom also occurs because of other than NATS malfunction, so start the trouble diagnosis according to SEC "Work Flow".
If ECM other than genuine part is installed, the engine cannot be started.

For ECM replacement procedure, refer to EC "Removal and Installation".

PRECAUTIONS FOR KEY REGISTRATION

The ID registration is a procedure that erases the current NATS ID once, and then registers a new ID. Therefore before starting the registration operation, collect all registered Intelligent Keys from the customer.
When registering the Intelligent Key, perform only one procedure to simultaneously register both IDs (NATS ID and Intelligent Key ID).

SECURITY INDICATOR LAMP

Security indicator lamp warns that the vehicle is equipped with NATS.
Security indicator lamp always blinks when the ignition switch is in any position other than ON.

NOTE: Because security indicator lamp is highly efficient, the battery is barely affected.

ENGINE START OPERATION WHEN INTELLIGENT KEY IS CONTACTED TO PUSH-BUTTON IGNITION SWITCH

When brake pedal is depressed while selector lever is in the P position the BCM activates NATS antenna amp. that is located behind push-button ignition switch.
When Intelligent Key (transponder built-in) backside is contacted to push-button ignition switch, BCM starts NATS ID verification between BCM and Intelligent Key (transponder built-in) via NATS antenna amp.
When NATS ID verification result is OK, buzzer in combination meter sounds and BCM transmits the result to ECM.
BCM turns ACC relay ON and transmits ignition power supply ON signal to IPDM E/R.
IPDM E/R turns the ignition relay ON and starts the ignition power supply.
IPDM E/R turns the starter control relay ON for engine starting in advance.
BCM detects that the selector lever position and brake pedal operation condition.
BCM transmits starter request signal to IPDM E/R and turns the starter relay in IPDM E/R ON if BCM judges that the engine start condition* is satisfied.
Power supply is supplied through the starter relay and the starter control relay to operate the starter motor.
When BCM receives feedback signal from ECM indicating that the engine is started, BCM transmits a stop signal to IPDM E/R and stops cranking by turning off the starter motor relay. (If engine start is unsuccessful, cranking stops automatically within 5 seconds.)

*: For the engine start condition, refer to "IGNITION SWITCH POSITION CHANGE TABLE BY PUSH-BUTTON IGNITION SWITCH OPERATION" below.

IGNITION SWITCH POSITION CHANGE TABLE BY PUSH-BUTTON IGNITION SWITCH OPERATION

The ignition switch position can be changed by the following operations.

NOTE:

When an Intelligent Key is within the detection area of inside key antenna or when Intelligent Key backside is contacted to push-button ignition switch, it is equivalent to the operations below.
When starting the engine, the BCM monitors under the engine start conditions,