Dongfeng Nissan Teana Car Maintenance Notes 2

Case 1

Fault phenomenon: A 2009 Dongfeng Nissan Teana car, equipped with a VQ25DE engine and a REOF10A continuously variable transmission, with a mileage of 982 km. The car was towed to a service station for repair because it lost the power steering function.

Inspection and analysis: First verify the fault phenomenon. It feels very heavy when turning the steering wheel, and there is a slight improvement when refueling. The car uses EPS electronic control hydraulic steering system. When doing a basic inspection of the vehicle, it was found that the power steering oil was leaking, but the power steering oil in the oil tank was still within the standard range. Connect Nissan’s special fault diagnosis instrument CONSULT-3 to enter the fault diagnosis. There is no fault code storage in each system, and no abnormality is found in the data flow. In line with the principle of starting with the easy and then the difficult, the resistance of the power steering solenoid valve is first measured to be 4.8 Ω, which meets the specified 4-6 Ω standard, and the fault of the solenoid valve can be preliminarily ruled out. Since the power steering solenoid valve and the steering gear are an assembly, the steering gear must be removed before the solenoid valve can be checked or replaced. So after lifting the faulty vehicle to the working height, the maintenance personnel started the engine on the vehicle. The author observed the power steering pump under the vehicle and found that as the engine speed increased, there were obvious oil drops from the front of the power steering pump. At this time, it can be determined that the power steering function failed due to the pressure relief of the steering pump.

Figure 1

Troubleshooting: Replace the power steering pump (Figure 1), and the power steering function returned to normal after the test run.

Case 2

Fault phenomenon: A 2009 Dongfeng Nissan New Teana sedan, equipped with a VQ25DE engine and a REOF10A continuously variable transmission, with a mileage of 9,500 km. According to the user, the ABS fault warning light on the dashboard of the vehicle is always on.

Figure 2

Inspection and analysis: First, use the Nissan special fault diagnosis instrument CONSULT-3 to read the system fault code. The current fault code C1107 (Figure 2) is stored in the ABS control unit, which means “right front wheel speed sensor-2”. After communicating with the user, it was learned that the ABS fault warning light was on after an emergency brake during driving. According to the user’s description, the maintenance personnel suspected that the fault was caused by the dirty or damaged wheel speed sensor, so they cleaned the wheel speed sensor and the signal disk on the wheel hub bearing, but the fault still existed after cleaning.

The author analyzed the stored fault code, because the right front wheel speed sensor -2 means that the right front wheel speed sensor circuit is short-circuited, or the distance between the speed sensor and the signal disk is too large, and the ABS control unit cannot recognize the sensor pulse. Possible causes of the fault include faults in the wheel speed sensor circuit and the signal disk, because the maintenance personnel have checked the relevant circuits and sensors, and no problems were found on the bearing surface. At this time, the maintenance personnel said that a piece of wool was found in the wheel hub bearing. Wrapped in the signal disk, the work light was used to check and found that the signal disk had gaps and wear. The right front wheel bearing was removed and it was found that the bearing magnetic ring had relatively serious wear (Figure 3), and the magnetic powder had all fallen off.

Figure 3

Troubleshooting: After replacing the right front wheel bearing assembly, the test run fault was completely eliminated.

Review and summary: When we repair some vehicles that have stored fault codes, we must be clear about the meaning of the fault codes, otherwise we will have to take many detours during the maintenance work or it will be difficult to find the faulty part.