BMW E90 Fog Lights With Flash and High Beam: the LH_ and FL_ Parameters

From the factory, the E90 switches the front fog lights off when the high beam is flashed. The line that removes that behaviour is LH_UND_NSW_NICHT_GLEICHZ in the light module. Keeping the fog lights lit under a continuously burning high beam is a separate parameter, FL_UND_NSW_NICHT_GLEICHZ, and confusing the two produces no result. What is the difference between the two parameters? The names are strings of German abbreviations. LH stands for Lichthupe, the headlight flash you make by pulling the stalk towards you. FL stands for Fernlicht, the high beam you switch on steadily by pushing the stalk forward. NSW is the front fog light and NICHT_GLEICHZ is the condition of not being lit at the same time. Both lines enforce the restriction at aktiv and lift it at nicht_aktiv. Module: FRM or NFRM (the source also carries a second LMA record) For the headlight flash: LH_UND_NSW_NICHT_GLEICHZ FRM/NFRM: 2008, 2009, 2010, 2011 LMA: 2008, 2009, 2010 For a continuous high beam: FL_UND_NSW_NICHT_GLEICHZ FRM/NFRM: 2008, 2009, 2010, 2011 Factory value: aktiv (never together) New value: nicht_aktiv (allowed together) Risk: low as a coding change, but use is bound by traffic law Which module and which years? The source list marks both parameters under the FRM or NFRM module for 2008 through 2011. LH_UND_NSW_NICHT_GLEICHZ additionally appears in a second record under the LMA module for 2008, 2009 and 2010. Across the E90 family the exterior lighting functions are gathered in the FRM or NFRM module, so read your own light module first and see which lines are actually present. • LH_UND_NSW_NICHT_GLEICHZ governs the flash case: marked for 2008-2011 under FRM/NFRM and 2008-2010 under LMA. • FL_UND_NSW_NICHT_GLEICHZ governs the continuous high beam case: marked for 2008-2011 under FRM/NFRM. • Only meaningful on cars fitted with front fog lights. • Model-year coverage comes from community-compiled E90 coding lists; the binding source is your own car's FSW/PSW data. How do you code it? Decide first which case you want: fog lights during a flash only, under a steady high beam only, or in both. OBDThink is an independent BMW coding and diagnostics app and is not affiliated with BMW AG. Back up the current lighting coding before writing, because the light module also holds headlight type, country setting and indicator behaviour. • Confirm the fog lights already work, then switch the ignition on without starting the engine. • Connect with OBDThink and select your car's light module. • Read the coding data and save a backup before changing anything. • For fog lights during a flash, set the LH_UND_NSW_NICHT_GLEICHZ line to nicht_aktiv. • For fog lights under a steady high beam, set FL_UND_NSW_NICHT_GLEICHZ to nicht_aktiv as well. • Start the write and do not touch the ignition until the completion message appears. • Switch the fog lights on, flash the high beam and then hold it steady, checking each case separately. Watching live lamp output status in OBDThink shows whether the fog lights are actually being supplied, without staring at a garage wall. How do you revert it? Reverting means returning the line you changed to aktiv. If you touched both lines you have to revert both, otherwise the factory behaviour is only half restored. Where a pre-coding backup exists, restoring it returns both lines in one step. Module: your car's light module Restore the flash restriction: LH_UND_NSW_NICHT_GLEICHZ = aktiv Restore the high beam restriction: FL_UND_NSW_NICHT_GLEICHZ = aktiv Method: change the values and write, or restore the pre-coding backup Check: flash the high beam, the fog lights should go out What are the legal limits on fog light use? In many European countries front fog lights may only be used when visibility is markedly reduced by fog, heavy rain or snow. Driving with them in clear weather dazzles oncoming drivers and attracts a fine in some jurisdictions. This coding removes a technical restriction; it does not change the rule governing use. In fog it is the high beam that is the problem: its beam scatters back off the droplets and dazzles you with your own light. Drive on dipped beam with the fog lights and keep the high beam off. This coding is meant for a clear night, not for use in fog. What if the fog lights still switch off? The first thing to check is whether you changed the right line: the flash case belongs to LH_UND_NSW_NICHT_GLEICHZ and the steady high beam case to FL_UND_NSW_NICHT_GLEICHZ, and the wrong line produces no result. Second, read the light module coding data back and confirm the value was written as nicht_aktiv. Third, if front fog lights are not declared in your car's vehicle order, the module never drives those lamps.