Start of production to U0437000 V1 FROM U0437000 to U3000000 V2 FROM U3000000 to U4000000 V4 FROM U4000000 to EOP V5 no Dongle NATS V1 In 1994 NATS 1 was launched. It was designed to be an after-market fit to some petrol vehicles via pre wired connectors. It will immobilise the vehicle by interrupting three circuits. 1. Fuel Pump Relay 2. Camshaft Position Sensor 3. Ignition feed to the Engine ECM IMMOBILISER OPERATION The system can be Armed in two ways Passive (Automatic) or Active. Passive arming will take place 30 seconds after the ignition has been turned off and a front door has been opened. Active arming will occur when the ignition is switched off and the lock button is pressed on the remote fob. The system can only be Disarmed by pressing the unlock button within range of the control unit. The Keyfob transmits a complex rolling code to the (Smart Entrance Control Unit) SECU. When they are first produced the keyfobs are identical and need to be coded to the SECU. This can only be achieved with CONSULT loaded with the correct level of software and the NATS V1 interface. The LOCK and UNLOCK buttons can be pressed 100 times out of range of the vehicle and still work, if the buttons are pressed more than 100 times, if the battery is replaced or the vehicle battery is disconnected then the transmitters will need to be re-synchronised to the SECU. Re-synchronising is achieved by pressing the LOCK button 4 times in range of the vehicle. When the SECU receives a recognised code from a key fob it will communicate with the immobiliser relay by using a pulsed signal at 250Hz. On vehicles with alarms or keyless entry systems this is the also the arm/disarm command. Remember to disarm the immobiliser before carrying out engine diagnosis with Consult. Once the SECU receives an ignition feed there is no communication with the key fob to prevent the immobiliser from being activated while the engine is running. If the SECU fails while the engine is running it will not immobilise the vehicle. Once the ignition is turned off the vehicle will remain immobilised until the concern has been rectified. NATS V2.0 PETROL The Nissan Anti-Theft System (NATS) Version 2.0 incorporates an immobiliser control unit (IMMU) which provides a complex coded link to the ECCS engine control module (ECM). It is factory fitted and forms an integral part of the vehicle electrical system. Its operation s passive to the user and is achieved by means of a transponder (chip) moulded into the ignition key. The transponder sends a coded signal to the immobiliser control unit when the ignition is switched on. The immobiliser control unit sends a different coded signal to the ECCS engine control module that allows the engine to run. IMMOBILISER OPERATION The system is armed and disarmed by means of the transponder moulded into the ignition key. A NATS security indicator lamp (LED) will blink when the system is armed and will switch off when the system is disarmed. Since the transponder in the key is energised by a magnetic field generated by the antenna amplifier, no battery is required. A maximum of four keys may be registered to one immobiliser control unit. A failure in the NATS system will be indicated by blinking of the malfunction indicator lamp (MIL) which is located in the combination meter of the instrument panel. If both the NATS and ECCS systems or just the ECCS system is malfunctioning, the MIL will illuminate constantly. ENGINE START CONDITION When the ignition is switched on, the immobiliser control unit delivers power to the antenna amplifier. The ECCS engine control module instructs the immobiliser control unit to request the ID code of the transponder in the ignition key. The antenna amplifier generates a small magnetic field to energise the transponder (the operation distance is approximately 3 - 4 cm, which makes "grabbing" almost impossible). If a correct code is received, the immobiliser control unit sends its own ID code to the ECCS engine control module. If the ECM receives the correct code, the engine systems are enabled. If an incorrect code is received from either the transponder or immobiliser control unit, the ECCS ECM will not allow the engine systems to operate, (immobilised) and the MIL will blink. If a non-initialised immobiliser control unit (with matching transponder) is used to try and start the engine, the ECCS ECM will make a total of 5 requests for a correct ID code. Unless the correct ID code is received twice during this time, the engine system will be disabled. No further codes are accepted until the ignition is switched off and then back on. ENGINE STOP CONDITION Each time the ignition is switched off, the ECCS ECM sends a new code to the immobiliser control unit. This code is memorised in preparation for the next start procedure (rolling code). INITIALISATION USING CONSULT During initialisation, an initialisation request is sent from CONSULT to the ECCS ECM. After receiving this request, the ECCS ECM initialises a rolling ID code and sends an initialisation request to the immobiliser control unit. The immobiliser control unit now memorises the key ID and sends an "initialisation complete" signal to CONSULT. NATS V4.0 PETROL AND ECCS-D To simplify the system and improve reliability, the antenna amplifier and immobiliser control units are combined in one unit. The NATS ignition key incorporates a cryptograph transponder instead of a fixed code type. This new device improves the anti-scan function and cannot be copied. IMMOBILISER OPERATION When the ignition is switched on, the ECCS ECM requests the immobiliser control unit to send a code to the transponder. The antenna amplifier energises the transponder in the NATS ignition key and the IMMU sends a cryptographic challenge to the transponder. The transponder then sends a cryptographic response back to the IMMU, which determines whether the response is correct. If they are, the IMMU sends another code to the ECM, which allows the engine to start. When the ignition is switched off, the ECM sends a new code to the immobiliser control unit. This code is memorised in preparation for the next start procedure (rolling code). Each time the ignition is switched on, a different cryptographic challenge is sent from the IMMU to the transponder. NATS 5.0 NATS 5.0 is based on the NATS 4.0 system, but differs from it in the following areas: The communication protocol between the ECM and the immobiliser is completely new for NATS 5.0. It operates at a much higher speed and will verify a key in less than 750ms. The NATS ignition key incorporates a cryptograph transponder instead of a fixed code type. This new device improves the anti-scan function and cannot be copied. Immobiliser Operation When the ignition is switched on, the ECCS ECM requests the immobiliser control unit to send a code to the transponder. The antenna amplifier energises the transponder in the NATS ignition key and the IMMU sends a cryptographic challenge to the transponder. The transponder then sends a cryptographic response back to the IMMU, which determines whether the response is correct. If they are, the IMMU sends another code to the ECM, which allows the engine to start. When the ignition is switched off, the ECM sends a new code to the immobiliser control unit. This code is memorised in preparation for the next start procedure (rolling code). Each time the ignition is switched on, a different cryptographic challenge is sent from the IMMU to the transponder. The rolling code between the ECM and the immobiliser is replaced by a cryptographic challenge-response system (similar to the NATS 4.0 transponder to immobiliser). The transponder (TPOK) signal is more secure than the signal on NATS 4.0. The TPOK signal is also sent to the Timer Control Unit (TCU) for additional functions such as releasing super lock or switching the alarm off. System initialisation is only possible using CONSULT-II. It is necessary to enter a 4 digit PIN number into CONSULT-II before initialisation can be started. Each vehicle has a unique code that is supplied on a card similar to that for the audio code. An audio personalisation function is incorporated. The transponder code is sent to the audio system to set up audio preferences. Different audio settings can be assigned to different ignition keys. The NATS Security LED is used to indicate the status and any malfunction of the immobiliser system. The description is in the service manual.