Interpretation of Dongfeng Nissan March Sedan’s Technical Highlights

MARCH is a mini family sedan recently launched by Dongfeng Nissan Motor Company. The car is equipped with a 1.5L engine and is matched with a 4-speed automatic transmission and a 5-speed manual transmission. In order to facilitate readers’ understanding of the car, some of its technical highlights are introduced here.

1. Automatic transmission

MARCH Sedan is equipped with RE4F03C 4-speed electronically controlled automatic transmission (Figure 1). This transmission has been improved in many places compared with the old transmission.

Figure 1

1. Mechanical system

(1) Mechanical structure and size

Compared with the old transmission, the new transmission improves the structure of the automatic shift mechanism and the characteristics of the transmission components, making the transmission smaller and the weight reduced by 15% (Figure 2).

Figure 2

(2) Torque converter

The torque converter used in this car is smaller than the torque converter used in TIIDA (Figure 3). While ensuring the smooth operation of the engine, the mass of the transmission can be reduced to improve the fuel economy of the vehicle.

Figure 3

2. Automatic transmission control system

(1) CAN communication control

This transmission adopts integrated control of the engine and automatic transmission to improve the shifting feel. During sudden start and acceleration, the engine output control signal is transmitted between the ECM and TCM (Figure 4), and real-time coordinated control is achieved according to driving conditions.

Figure 4

(2) Shift control

When the throttle opening is large, when shifting from 1st gear to 2nd gear or from 2nd gear to 3rd gear (sudden start or sudden acceleration), the TCM sends a request signal to the ECM to reduce the torque output. According to the torque reduction request signal, the ECM will delay the ignition timing to temporarily reduce the engine output torque. At the same time, the TCM will use the vehicle speed sensor to track the situation in the transmission so as to achieve the shift control at the best shifting time.

(3) Self-diagnosis function

If the automatic transmission control system fails, the fault code can be read through the diagnostic instrument or the OD-OFF indicator. If there is no fault in the control system, when the ignition switch is turned on, the OD-OFF indicator will light up for 2 seconds and the solenoid valve check will be performed.

By inputting the self-diagnosis start signal, the fault code is output and the OD-OFF indicator light on the instrument cluster flashes to indicate the fault location. If there is a fault, the indicator light corresponding to the fault area will light up for a long time (Figure 5). When the ignition switch is turned off after completing the self-diagnosis, the indication of the fault area will be cleared.

Figure 5

II. Body electrical system

1. Central door lock system

The central door lock system of this vehicle is controlled by the BCM. Each door can be locked/unlocked by operating the driver’s side door lock cylinder, the driver’s side door lock knob and the central door lock switch. After the key is inserted in the ignition lock cylinder and the driver’s side door is opened, when the driver’s side door lock knob or the central door lock switch is operated to lock, the door will open immediately after locking to prevent the car key from being locked in the car. When the driver’s side door lock knob is locked, when the inner handle is pulled, it only opens the driver’s side door lock and the door can be opened.

(1) Central door lock control system control principle diagram

The central door lock control system control principle diagram is shown in Figure 6.

Figure 6

(2) Main components of the system

①BCM

BCM controls all door lock actuators based on the signals from the central door lock switch and the driver’s door lock detection switch (integrated in the driver’s door lock actuator).

②Central door lock switch

When the door is locked/unlocked, a signal is sent to the BCM.

③Door lock actuator

The door lock actuator is installed in the door lock of each door and locks or unlocks each door through the lock/unlock signal from the BCM.

④Key insertion detection switch

The key insertion detection switch detects the insertion of the key and sends a signal to the BCM.

2. Remote control door lock system (non-intelligent key control system)

The remote control transmitter (integrated with the key) sends radio waves, the remote control receiver receives the signal, and sends the signal to the BCM. The BCM checks the remote control ID and locks/unlocks the door only when it matches.

When the door is locked/unlocked by the remote control, the hazard warning lights flash as an operation check. When the door is unlocked by the remote control, the interior light control function turns on the interior light through a timer, and when the door is locked, the interior light is turned off. The control principle diagram of the remote door lock system is shown in Figure 7.

Figure 7

In the case of a lost remote control, a new remote control can be registered up to 5 times. The remote control ID can be manually registered using the key, or the ID can be registered, checked and cleared using a diagnostic instrument.

3. Smart Key System

The smart key system enables the driver to lock/unlock the door and start the engine without a key, which is performed through two-way communication between the smart key and the vehicle.

Figure 8

When the smart key unit detects that one of the request switches is pressed, it activates the external and internal antennas corresponding to the pressed door request switch. The activated antenna transmits the request signal to the smart key and checks whether the smart key is near the door and whether it is outside the vehicle. When the smart key is within the external antenna detection area (Figure 8), the smart key receives the request signal and sends the key ID to the smart key unit. The smart key unit receives the key ID signal and compares it with the ID registered in the vehicle. If the key ID check result is OK, the smart key unit sends the door lock or unlock request signal to the BCM through the CAN communication bus. When the BCM receives the door lock or unlock signal, it starts the door lock actuator and flashes the hazard warning light for a working check.

When the smart key system fails, bring the smart key close to the window at the bottom of the “start button” (Figure 9) and press the “start button” at the same time to enable the NATS backup system in the ignition key so that the vehicle engine can start normally.

Figure 9

4. NATS anti-theft system

All MARCH models use Nissan’s dedicated engine anti-theft system NATS as the anti-theft control device, and the security indicator light is installed in the instrument cluster (Figure 10) and controlled by the BCM. Each mechanical key is assigned an ID code, and only those keys with IDs registered in the BCM and ECM can start the engine.

Figure 10

Starting the engine with the smart key is controlled by the BCM. If the customer needs, up to 5 keys (including the standard key set) can be registered. When registering the key ID after repair, replacement of parts or adding a mechanical key, the previously used registered mechanical key must be registered again. Therefore, all keys must be obtained from the user first.

5. Power window system

(1) Power window control system schematic

The power window control system schematic is shown in Figure 11.

Figure 11

(2) Anti-pinch function

If the driver’s side power window is pinched by an obstacle when it is rising, the window will drop 150 mm. When the driver’s side door is subjected to an impact or load equivalent to an obstacle being pinched, the window may drop depending on the environment and driving conditions.

Figure 12

The driver’s side power window motor conventional system has a limit switch and a pulse sensor. In the power window motor drive system of this vehicle, the limit switch has been removed and two pulse sensors (Figure 12) are installed to simplify the structure. To control the system, information on the glass position and the direction of glass movement is required. Therefore, if the system loses position information or fails in position information during inspection or maintenance, the system must be initialized.

Figure 13

The power window switch detects the movement of the glass by counting the number of pulses sent by pulse sensor 1 for each rotation of the motor shaft. Then, it detects the difference in the pulse signal of pulse sensor 2 to determine the direction of movement of the glass (Figure 13). The power window main switch reads pulse sensor signals 1 and 2 to determine the state of the door glass and perform control operations. When the power window is raised by automatic control or when the ignition switch is in a position other than ON (when the timer is turned on), if an obstacle is caught and a fixed load or greater force acts on the driver’s side door glass, the signal of pulse signal sensor 1 changes. The power window switch reads the change in the signal, stops the upward movement of the power window motor, and transmits a downward signal to lower the driver’s side door glass by a fixed amount.

Figure 14 Waveform signal when the anti-pinch function is activated

(3) Failure protection function

When the driver’s side door glass rises, if the decoder signal that detects the direction of movement is detected to be irregular, or if a fault is detected between the fully closed position of the glass stored in the electric window switch and the actual position of the glass, the fail-safe control operation is entered, and the system is in a non-initialized state.

(4) Setting method of the driver’s side electric window anti-pinch function

After completing the following operations, initialize the driver’s side electric window:

① Initialization procedure:

a. Turn the ignition switch to the “ON” position;

b. Open the door glass halfway or more;

c. Operate the electric window switch to move upward, and when the glass stops at the fully closed position, press the switch for 3 seconds or more;

d. If the opening and closing operations are performed continuously for more than 10 times, the anti-pinch function may fail.

Note: Before performing the initialization procedure, be sure to disconnect the battery terminal or the electric window switch plug.

②Cancel the anti-pinch function procedure

Method 1: Turn the ignition switch to the “ON” position, open the door glass halfway or more, disconnect the plug of the power window motor and operate the power window switch upward for 1 s or more.

Method 2: Disconnect the battery plug for a while.