Troubleshooting of two line faults in Dongfeng Nissan Teana and Tiida

Case 1

Fault phenomenon: A 2006 Dongfeng Nissan Teana 2.5L sedan, which uses Nissan NATS anti-theft system and has a keyless start function. The car was repaired in a newly built service shop, and the maintenance personnel asked the author for help, saying that the car’s smart key could not be registered.

Inspection and analysis: After communicating with the other party’s maintenance personnel, the author learned that except for the inability to register the smart key, the other functions of the car are normal, the system can also find the smart key in the car, and the unregistered key also displays normally. Therefore, the possibility of faults in the body control unit BCM and the smart key control unit can be basically ruled out. Based on experience, the author judged that the fault may be related to the antenna in the car.

Figure 1

Since the other party had no relevant maintenance experience, the vehicle was driven to the author’s service shop for inspection. The author used Nissan’s special fault diagnosis instrument CONSULT-Ⅲ to test the relevant system, and no fault code was found to be stored. When registering the key, a prompt that the registration could not be performed appeared. The Nissan NATS system receives the signal of the smart key through three internal antennas and three external antennas (Figure 1), and then feeds back to the body control unit BCM to control the unlocking and locking of the car door, the starting of the ignition switch, and the key registration function.

The author analyzed that the antennas related to registration mainly include antenna 2 inside the dashboard and antenna 1 in the central console, and their main functions are the use of the smart key and the reception and feedback of the registration signal. Since the two antennas are in the dashboard and the central console, it is more troublesome to disassemble them. In order to confirm my judgment, the author used a fault diagnosis instrument to actively test the antenna in the smart key unit, put the smart key in the car, turn off the ignition switch to perform an active antenna test, and found that only antenna 1 did not respond after being turned off. As long as the other antennas were disconnected, the emergency lights would flash. In this way, the fault location can be basically determined, so it was decided to check antenna 1. Remove the trim panel behind the central console, find the indoor antenna 1, and find that there is no plug on the wiring harness socket on the antenna (Figure 2).

Figure 2

Troubleshooting: Find the wiring harness plug of the antenna (Figure 3) and find that it is pressed under the floor glue. Remove the floor glue, find the plug to connect to the antenna, re-register the smart key, and the system shows that the registration is successful.

Figure 3

Review and summary: When repairing some electrical system faults, it is important to be familiar with the components of the system so that the cause of the fault can be found quickly.

Case 2

Fault phenomenon: A 2007 Dongfeng Nissan Tiida 1.6L sedan, equipped with an HR16DE engine and a 5-speed manual transmission, with a mileage of 50,000 km. According to the user, the engine fault light on the instrument of the car is on.

Figure 4

Inspection and analysis: Use Nissan’s special fault diagnosis instrument CONSULT-Ⅲ to read the fault code and store the fault code P0335 (crankshaft position sensor circuit). The maintenance personnel checked the relevant circuits but found no problems, so they cleared the fault code and handed the vehicle to the user. The next day, the user entered the factory for repair because the engine fault light was on. The maintenance personnel used an oscilloscope to collect the signal waveform of the crankshaft position sensor (Figure 4) and found no abnormality; the crankshaft position sensor, refrigerant pressure sensor and engine control unit related to the fault were replaced successively, but the fault phenomenon did not change.

So the author decided to confirm the engine wiring harness again. When checking the connection of each harness and plug, it was accidentally found that the plug of the engine control unit was abnormal, and one side of the buckle could not be locked (Figure 5).

Figure 5

Troubleshooting: Repair the plug that cannot be locked, and test drive troubleshooting.

Review summary: Due to the separation of the plug buckle of the engine control unit, the ECM pin cannot be inserted in place. When the vehicle is bumpy, the plug sometimes has poor contact, causing the engine fault light to light up.