Model: F02 with N52 engine.

Mileage: 90888km

Fault phenomenon: the customer reported that the door lock of the main driving car could be closed but could not be opened, and the other three doors could not be opened or closed.

Fault diagnosis: see the fault phenomenon, and empirically judge the power supply, lock block fault or JBE fault of the central control lock.Vehicle test has fault code:

Central control lock of 80209B: remove interlock relay damage or fuse break

80209D central lock: the interlock relay is damaged or the fuse is broken

ABL prompt check power fuse F14 15A and F15 20A fuses.

Inspection found F14 insurance fuse broken, F15 normal.After the replacement of F14, the central control lock function is normal.Similar faults were encountered before. In order to determine which lock block was the fault, a 5A fuse was connected in series from JBE to the four door lock block and the motor control line of fuel tank cover. Half a year later, the fuse of the right front door lock block blew out, indicating that the right front door lock or circuit had short-circuit fault.

However, the method of series fuses is too cumbersome, so I gave the customer a quotation of 4 lock blocks, but the customer did not agree because of the cost problem, so we must let us determine which lock block problem.

After analyzing the circuit diagram, as shown in figure 1, it was decided to adopt the method of measuring the current and resistance of the lock block to determine the fault.

Figure 1 F14 fuse control circuit

MZS deadlocked motor control, MER deadlocked and locked motor sharing line, MVR motor control line.The deadlocked motor current can be determined by measuring the MZS line current.By measuring the MER wire you can determine the total current when the lock is opened.The current of the locked motor can be determined by measuring the MVR line.From the current size, it is not only possible to determine which lock block fault, but also further determine which motor damage caused.Test the MER line current of normal vehicles, as shown in figure 2. The maximum is 2.57a and the minimum is 2.53a.

Figure 2 test the current of MER line (normal)

Normal vehicle test MVR line current, as shown in figure 3, is 1.54a at the maximum and 1.49a at the minimum.

Figure 3 test MVR line current (normal)

The current of MER line at the right front door of the defective car is shown in figure 4, the maximum current is 3.47a, and the minimum current is 3.41a.

Figure 4 MER line current

The MVR line current of the right front door of the defective car is shown in figure 5, the maximum current is 2.36a, and the minimum current is 2.13a.

Figure 5 MVR line current

Through measured four door lock on the block MZS, killing, MVR line current, and finally found the right front door lock motor current is too high, more than the normal standard of current car, in the state of fault measuring just 3.7 Ω trouble truck locked motor resistance, the normal car around 10 Ω, so you can determine the right front door lock piece of locked inside the motor due to the internal coil short circuit or resistance is occasionally lead to high current and make the F14 blown fuse.Replace right front door lock block for troubleshooting.

Fault summary: although it is an accidental fault, it can also be found that the aging of the lock block motor causes the current higher than the standard range after comparison with the normal car.

It is impossible to determine the control relationship between F14 and F15 fuses and the lock block circuit from the circuit diagram, but from the phenomenon, F14 fuse damage leads to the left front door can be locked and cannot be unlocked, and the other three doors can neither be opened nor locked.The F15 fuse is damaged, so the left front door can be unlocked but cannot be locked. The other 3 doors can work normally, but 4 doors have no deadlock function.