Mercedes - fault codes U118A02, B178392, U120B97 - low beam does not switch off

Data sheet
ManufacturerMercedes
Vehicle model167/177/213/238/257
Year of manufacture2017 - 2020
Special featuresModels with LED headlights
SymptomsLow beam does not switch off, High Beam Assist not operational; fault codes U118A02, B178392, U120B97

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

In the Mercedes 167/177/213/238/257, a software error in the headlamp control unit may lead to various symptoms

In the above-mentioned vehicles, a software error may cause one headlamp to remain sporadically on after the lights have been switched off.

 

At the same time, a warning message appears on the multifunction display:

  • Low beam faulty
  • Adaptive High Beam Assist not operational

 

In parallel, the following fault codes are often stored in the headlamp control unit:

  • U118A02 (headlamp levelling malfunction)
  • B178392 (LED drive module fault)
  • U120B97 (headlamp malfunction)

 

In an effort to rule out other causes, check all possible system components and read out/delete the fault memory.

 

If no errors are identified, update the software (parameter calibration by recoding) of the headlamp control unit. We advise to contact a Mercedes-Benz workshop for this purpose.

Please note

This information may also apply to other models and years of manufacture.


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