BMW F02 Door Locking/unlocking 80209D Trouble Repair

One of my vehicle repair workshop friend share his experience for BMW door trouble repair.He described that a BMW F02 with 100,000 km equipment with N52 engine get trouble on door locking.The driver side door can be locked with main control panel but can not unlocked,and other 3 doors neither locking or unlocking with main control panel.More repair cases about BMW,please check here:BMW Trouble Repair

 

Diagnostics:

Use BMW ISTA diagnostic software scan the systems,got the below DTCs:

80209B and 80209D:Central locking: relay, unlocking faulty or fuse open

ABL prompt to check the F14 15A fuse and F15 20A fuse,after then mechanic found the F14 fuse broken and F15 work fine.

 

After replacing F14 fuse,the central control function work normally,and the problem disappeared.He has encountered a similar fault before,in order to make sure which component damaged,a 5A fuse was connected in series with the JBE to 4 doors lock block and the fuel tank cap motor control line.After half years later,right front door fuse blown,it hints there is a short circuit fault in the right front door lock or circuit.After replace the right front door lock,the trouble fixed.

 

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

We can measure the current of MZS,MER,MVR at door motor different status to ensure which motor trouble

 

By measuring the currents on the MZS, MER, and MVR lines on the four door lock blocks one by one, it is finally found that the current of the right front door is too high when locking.

 

In the fault state, the resistance of the locking motor of the faulty car is only 3.7 Ω, while the resistance of the normal car is about 10 Ω. Therefore, it can be determined that the internal coil of the locking motor in the right front door lock block is occasionally short-circuited or the resistance is too high, resulting in excessive current. Blown the F14 fuse.

 

After replace the front right door lock block and troubleshoot

Fault summary: Although it is an occasional fault, after comparing with normal cars, it can be found that the aging of the lock block motor causes the current to exceed the standard range.From the circuit diagram, there is no way to determine the control relationship between the F14 and F15 fuses and the lock block circuit, but from the perspective of the phenomenon, the F14 fuse is damaged and the left front door can be locked and cannot be unlocked, and the other two doors cannot be opened or locked; the F15 fuse is damaged As a result, the left front door can be unlocked but not locked, and the remaining three doors can work normally, but none of the four doors has a deadlock function.