Benz W176 B177655 LED Daylight Trobule Repair by Launch X431

After replacing headlight for Benz A-class W176,the LED daylight will not working correctly.And if you scan DTC in the system,the trouble code B177655 will be found.So this instruction show you the procedures on how to use Launch X431 PAD V to solve it.

More information for Benz trouble repair,please refer to Mercedes Benz Trouble Repair.


B177655:Control unit “Actuation module,LED exterior lighting,left front” has a malfunction.The component is not configured.




Launch X431 PAD V/X431 PAD VII or X431 IMMO PAD



Connect Launch X431 PAD V to Benz car,then access Benz menu to make a full health report and check all DTC.

Benz-W176-B177655-LED-Daylight-Trobule-Repair-by-Launch-X431-3 Benz-W176-B177655-LED-Daylight-Trobule-Repair-by-Launch-X431-4


Select “SG-SW-HEADLAMPS”–>”Read Trouble Code”


Back to “SG-SW-HEADLAMPS” menu to select “Special Function”–>”Teach-in Processes”


Select “Commissioning of control unit “E1n7(Actuation Module,LED exterior lighting,left front)”


In the following sequence,the string of characters must be localized on the lamp unit for teaching in control unit “E1n7 (Actuation module,LED exterior lighting,left front)”.The string of characters must hen be entered into the diagnostic unit.


If the string of characters on the headlamp is recognized as faulty and is not accepted, please contact the User Help Desk. It is not permissible to enter another string of characters without being prompted to do so e.g. that of another headlamp. The headlamp can be(irreparably) damaged by an incorrect string of characters.

Click “Continue”


Commissioning of control unit “E1n7(Actuation module, LED exterior lighting, left front)”

Enter the string(without spaces or hyphens and in lowercase letters) with label”LAM-S-3K”into the following field. Press button

“Continue”to continue.

LAM-S-3K Enter string:******

The following requirements must be satisfied so that the string is clearly visible:

-The engine hood is open.-The headlamp is removed.

-The control unit “E1n7(Actuation module, LED exterior lighting, left front)”was removed.

-The string is located on the label inside the headlamp.

-The string must be 11 digits long.

-For example:1A 0017 5010AAIA8I

-The correct input of the string is:”a007500aaa8”.

Click “Input”


Input string of headlight control unit


Then press “Continue” and wait processing


After finishing,press “Continue”


Now back to menu to clear fault code,then read fault code again,you will find all work correctly.


More test report about Launch X431 please check:Launch X431 Test Report

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