Adjusting and replacing LED headlamps

Here you can find useful information and valuable tips on all aspects of replacing and adjusting an LED headlamp on a Mercedes-Benz W212.

The following information including service work shown is based on the example of a Mercedes-Benz W212 (model year 2014) but also applies to other vehicle models with identical component systems.

Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their work. The information provided on this website is intended for use by suitably qualified personnel only.

Requirements for vehicle lighting are steadily increasing, a fact which places high demands on vehicle lighting systems. LED headlamps with innovative light functions are integrated into the technical systems of modern vehicle models. The functions are monitored by higher-level control units. Even a seemingly simple replacement of a headlamp requires special work steps in order to carry out a professional diagnosis and repair.


The following information including service work shown is based on the example of a Mercedes-Benz W212 (model year 2014) but also applies to other vehicle models with identical component systems.  

System components


Design: 1. Plastic lens 2. Lens holder 3. 2*6 chip for LED light source 4. Vario roller with IHC+ functionality 5. CIPOS sensor system for the roller position


The 2*6 chip for LED module / range module generates a luminous flux of up to 2,765 lumens, whereby the road illumination optimally supports the driver with all the various light distributions.


Design: 1. Lens/ reflector lens holder 2. Carrier frame 3. Harness assembly 4. Thermal sensor 5. Contact element+LED 6. Heat sink


The 5 chip module for the immediate road surface in front of the vehicle generates a luminous flux of up to 1,260 lumens, which achieves homogeneous illumination “at close range”.


LED DI; light guide carrier with 8 LEDs and primary optics.


LED-DRL-PO light distribution, light guide technology.


Bulb shield or cover for targeted illumination of the cornering area.


The light control units control various functions, such as light functions, SW fan/thermal management, Vario LED module functions, etc.


In addition, the control units – together with the vehicle system – regulate light distributions for the driving situation via the CAN bus using the Vario LED module.

  • (Roller) adaptive light actuator
  • (Height adjustment) vertical light actuator
  • (Dynamic cornering light / swivel function) curve light actuator


As is the case with other electronic components, the powerful LEDs with their enormous light output from a comparatively small chip surface must be operated within certain temperature limits. To this end, robust fans specially designed for headlamp technology are integrated in an intelligent thermal management system.

Defective LED headlamp: Symptoms

The following effects can occur if LED headlamps fail:

  • Fault lamp lights up (system-dependent)
  • Fault entry in the relevant headlamp control unit

LED headlamp defective - the causes: Causes of failure

The following causes may be responsible for failure or malfunction:

  • Power supply faulty
  • External damage; accident
  • Vehicle system, CAN bus values implausible
  • Failure of headlamp electronics
  • Defective control unit
  • Defective headlamp fan

Checking LED headlamp: Troubleshooting

The LED headlamps or indeed vehicle lighting is monitored by higher-level control units. Any occurring errors are stored in the control unit's error memory and can be read using a suitable diagnostic device


With some vehicle models, a warning message can also be displayed on the instrument cluster in the event of a system error. However, before control unit diagnostics are undertaken, it is first advisable to carry out a visual check on the individual system components as part of initial troubleshooting activities. 

Control unit diagnostics

As part of control unit diagnostics, it is possible to employ the help of various functions and vehicle information as and when needed.

Error code  In this function, error codes stored in the error memory can be read. For subsequent troubleshooting, the error code description contains general information on possible effects or causes (Fig. 1).


Parameters In this function, current measured values from the control unit can be selected and displayed for the various light functions (Fig. 2).


Actuator test  In this function, vehicle-specific headlamp functions can be controlled separately (Fig. 3).

Adjusting LED headlamp: Instructions

Preparation for headlamp adjustment

Before the headlamps can be adjusted, the following work must be carried out on the vehicle: 

  • Check tyre pressure and correct if necessary.
  • Check load.
  • Ensure correctly calibrated vehicle level; for vehicles that were previously raised, roll/drive them a few metres before adjustment so that the chassis "springs in".
  • Put the steering wheel in "straight ahead" position.
  • Close all doors.
  • Read off the vehicle-specific forward inclination, in this case 1%.
  • Beamsetter to be set up and aligned in front of the vehicle, i.e. in front of the headlamp

The vehicle and the beamsetter must stand on level ground (with the headlamp setting location in accordance with country-specific requirements).


It is recommended to connect a suitable battery charger to support the vehicle electrical system.

Adjust the headlamp using the beamsetter

The various diagnostic options are shown as examples by the mega macs 77 diagnostic device. The respective test depth and variety of functions can be set out differently depending on the vehicle manufacturer and these are dependent on the relevant system configuration of the control unit.

Carry out the following steps on the diagnostic device / vehicle

Connect a diagnostic device and then set up a beamsetter in front of the vehicle.

  • Select vehicle
  • Switch on the ignition
  • Read out and clear error memory
  • Select basic setting "Adjust headlamp" 
  • Select zero setting 
  • Switch on headlamps
  • Confirm zero setting. This sets the headlamps to the basic setting "Adjust headlamp". 
  • Carry out headlamp adjustment, i.e. beam setting.

Set the dial and light pattern

Set the dial of the analogue beamsetter to 1%. Mechanically adjust the light pattern in the horizontal position (reference line of height adjustment) or the vertical cut-off line to the O° line (Fig. 4).


With the digital beamsetter, use the proven vehicle and headlamp system selection. Select the forward inclination 1%. Then using the digital guide lines, mechanically set correct adjustment of light pattern (Fig. 5).

Confirm new values

Following adjustment, confirm new values on the diagnostic device.

  • Secure vehicle to prevent automatic starting
  • Completely switch off the electrical system, remove the ignition key
  • Dismantle wheels, inner mudguards, bumpers
  • Disconnect electrical connections
  • Remove the headlamps
  • !!! ESD (electrostatic discharge) - guard against this when handling electronic components.
  • Attach the control units to the new headlamps at a separate workstation. Make sure that the connectors are correctly locked and that the seals are seated correctly. Observe tightening torques!
  • Adjust the height of the fixing banjo bolts between the old / new headlamp. When assembling, this is helpful in order to comply with the body gap dimensions/bumper headlamps.
  • Adaptation: in some cases it may be necessary to adapt the LED headlamp to the vehicle after mounting and before adjustment. In order to do this, a connection between the vehicle and the server of the vehicle manufacturer has to be set up. Connect the diagnostic device or VCI unit to the server in accordance with the manufacturer's specifications and follow the vehicle manufacturer’s instructions of use.  

Repair work on the lighting system in a vehicle may only be carried out by trained specialists. Repair work that is carried out incorrectly can lead to system failure and to severe personal injuries. For all repair work performed on the lighting system, please observe the safety and assembly instructions relating to the system in question and/or to those instructions provided by the relevant vehicle manufacturer.

Changing LED headlamp on a Mercedes-Benz W212: VIDEO

Replacement of a full LED headlamp on a Mercedes-Benz W212

In this video we show you how to professionally replace a full LED headlamp on a Mercedes-Benz W212 (model year 2014).

Replacing headlamp control units – flashing / coding control units: Instructions

After replacing the headlamp, individual components or the control units, it may be necessary to adapt or align the unit software to the respective vehicle periphery. Depending on the repair process, the LED code can be coded or new control units can be registered. These procedures are usually carried out online by means of a diagnostic device. This requires access authorisation to the online portal of the relevant vehicle manufacturer.


In our case study, the LED headlamp configuration is carried out, as an example, using a Hella Gutmann macsRemote diagnostic device and macsRemote Services.

Programming control units: Instructions

Programming, also called flashing, is carried out remotely using a suitable diagnostic device. The prerequisite is a stable connection to the server of the relevant vehicle manufacturer.


So, for example, after replacing a control unit, the following procedures and programming functions are carried out.


After connection to the vehicle, first of all vehicle identification and the codes of the control units are queried. Following successful identification, initialisation of the new control units is performed. In this automated process, the hardware, software status and the variant of the control unit are recorded and matched to the vehicle.


Depending on the vehicle and system configuration, the following adaptations are carried out in order to achieve operational status:

  • Update of the basic software
  • Control unit variant
  • Adaptation of the VCD vehicle data record segments 
    • Low beam
    • Active dynamic cornering light
    • Motorway light
    • High beam
    • Fog light, extended
    • Off-road light
    • Daytime running light
    • Warning light
    • Direction indicator light
    • Stepper motor parameters
    • Light colour LED configuration
    • Extended vehicle-specific data records


After successful programming, a test run is automatically carried out on the headlamp. In this reference run, the functions of the headlamp are tested (Fig. 01 to Fig. 04).

Flashing / coding LED headlamp control units: VIDEO

LED code: Instructions

The light colour of the LED lamps is also configured as part of the programming.


This function is necessary in order to optimally adjust the LED lamps of the new headlamp to the vehicle configuration.


The LED code is individually assigned to each individual lamp unit and appears on the headlamp housing. During programming, the LED code must be read and entered in the diagnostic application.


So as to avoid unnecessary delays while programming, photograph the LED code before beginning to mount the LED headlamp!

Coding of further functions: Instructions

Depending on the vehicle model and the region where the vehicle will be used, it may be necessary for the headlamps to be subsequently readjusted. Depending on the function, this can be done by the on-board electronics or by online support.


In this way, for example, country-specific requirements are adapted.


Country-specific requirements / regulations can involve, for example, the following switch-on conditions for the headlamp.

Light codes:

  • Daytime running lights switched on
  • Daytime running lights switched off
  • Daytime running light switched on + rear light switched on
  • Coming home, leaving home switched on
  • Coming home, leaving home switched off
  • Tourist light (driving in left-hand traffic with left-hand drive)
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