Mercedes - fault codes U118A02, B178392, U120B97 - low beam does not switch off
| Data sheet | |
| Manufacturer | Mercedes |
| Vehicle model | 167/177/213/238/257 |
| Year of manufacture | 2017 - 2020 |
| Special features | Models with LED headlights |
| Symptoms | Low beam does not switch off, High Beam Assist not operational; fault codes U118A02, B178392, U120B97 |
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.
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