How to Repair BMW Light Control Module (LCM) On E39

The Light Control Module is also shorted called LCM which manages all the individual lights of the car.It take a important role in the automobile illumination system.Many BMW owners found these symptoms:

1.Lights would turn on without the car running.

2.Main beam light stay on even if you have locked your car.

3.Have no lights at all on one side.

These problems are caused by a short circuit or interruption of an internal transistor in the LCM.You can ask dealers to replace the entire LCM,but it is $400,need to reset BMW Light Control Module and  reprogram it.As an alternative, you can simply replace the transistor Infineon BTS426L1.So in this guide,I will share How to Repair BMW Light Control Module (LCM) On E39.

Note:This guide is for educational purposes only! Use this guide at your own risk!

BMW E39 LCM Repair Gudie

Tools you need to repair BMW LCM:

1.Solder station.

2.Soldering wire

3.Unloader copperplated

4.8mm cage or key for removing the LCM

5.New transistor BTS426L1

BTS426L1T

Procedures of Repairing BMW LCM:

1.Disconnect the battery cables

2.You will locate the LCM under the right trim panel.

BMW E39 LCM Repair Gudie-1

3.You need an 8mm tool to unscrew the LCM

4.Disconnect the 3 connectors on the LCM.

BMW E39 LCM Repair Gudie-2

5.Open up the LCM.

BMW E39 LCM Repair Gudie-3

6.Open the tension clips which hold the transistors against the cooling flange.

7.Unscrew the cooling flange

8.Remove the cooling flange carefully from the effect transistors.

BMW E39 LCM Repair Gudie-4

9.The transistor is soldered on both sides.

10.Remove the transistor using the appropriate listed equipment with caution.

11.Solder in the new transistor

12Replace everything as a reversal of the removal procedure.

If you worry PCB will be damaged when you slolderig transistor,you would better to go to an electronic repair shop to ask for help.

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1 Comment

  1. Thank you for this big relief of an article. My question is, do o buy only one transistor Infineon BTS426L1 or 3 pieces as shown in your picture?

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