BMW E90 Seat Belt Chime: SBR Parameters and the Legal Picture

On the E90 the chime that sounds when a belt is unfastened is governed by SBR parameters inside the ABG module, the airbag control unit. The driver's side runs on SBR_FAHRER_1, while the passenger side uses SBR_BEIFAHRER_1 or SBR_BEIFAHRER_2_CD depending on model year. This is an intervention in a type-approved safety system. Which line covers which seat and which year? The source list defines three separate lines whose coverage partly overlaps: the 2008 model year is marked on all three, so for that year it is the iDrive/CIC generation, not the model year, that decides which passenger-side line applies. For the driver's side, SBR_FAHRER_1 is marked for the 2006, 2007, 2008, 2010 and 2011 model years. For the passenger side, SBR_BEIFAHRER_1 applies from 2006 to 2008, while SBR_BEIFAHRER_2_CD covers CIC-equipped 2008, 2009 and 2011 cars. Module: ABG (airbag control unit) Driver's side: SBR_FAHRER_1 — 2006, 2007, 2008, 2010, 2011 Passenger side: SBR_BEIFAHRER_1 — 2006, 2007, 2008 Passenger side (CIC): SBR_BEIFAHRER_2_CD — 2008, 2009, 2011 To disable: nicht_aktiv Risk: high — this writes to a safety module Why is this coding different from the others? ABG is the module that governs the airbags and the pyrotechnic belt tensioners. In the comfort codings covered elsewhere the worst outcome is a display that does not work; here a failed write can leave the airbag system in a fault state and light the airbag warning lamp in the cluster. • If voltage drops during a write to ABG, the module can be left in a fault state. • A car with the airbag warning lamp lit fails periodic inspection in most countries. • The coding concerns the audible chime only; it does not remove the legal duty to wear a belt. • 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? The change sets the relevant SBR line in the ABG module to nicht_aktiv. OBDThink is an independent BMW coding and diagnostics app and is not affiliated with BMW AG. Before touching this module, a battery charger should be treated as required rather than optional; a voltage drop mid-write has more serious consequences here than anywhere else. • Check the airbag system for stored faults before you code anything. • Attach a battery charger, switch the ignition on and do not start the engine. • Connect with OBDThink, select the ABG module and read the coding data. • Save a backup, then find the SBR line matching your car's model year. • Set the value to nicht_aktiv, write it, and touch nothing until the write completes. • Read the fault memory afterwards and confirm no new airbag fault appeared. Watching the belt buckle switch status live in OBDThink separates a chime silenced by coding from one silenced by a failed buckle switch. How do you revert it? Reverting means returning the same line to aktiv. If you saved an ABG backup before coding, restoring it is the preferred route. Returning the car to factory state before a sale, an inspection or a workshop visit is the cleanest approach. Module: ABG Line: the SBR parameter matching your car's year Revert value: aktiv Option 1: set the value to aktiv and write Option 2: restore the pre-coding ABG backup Check: switch the ignition on unbelted, the chime should sound again Inspection, legality and liability In Europe the seat belt reminder forms part of vehicle type approval under UN ECE R16; in North America it is regulated under FMVSS 208, where manufacturers self-certify rather than obtain type approval. Either way the reminder is part of the specification the car was certified and registered with, so switching it off is a change to a regulated safety device. The detail of the rules varies by country, so check your own national inspection regulations before coding. The duty to wear a belt continues regardless of this coding, and travelling unbelted is an offence in nearly every country. In a collision, being unbelted leads in many jurisdictions to compensation being reduced for contributory negligence; switching off the chime does not change that outcome, it only removes the reminder. • Periodic inspection checks safety system warning lamps; a lit airbag lamp fails the car. • In some countries an unapproved change to a type-approved safety device can affect the validity of the registration document. • Handing a used car over in factory coding spares the buyer an inspection problem. • Disabling the passenger chime hides the symptom of a faulty seat occupancy sensor chiming on an empty seat; a real sensor fault is still stored in the fault memory and lights the airbag warning lamp. What if the chime does not stop? First make sure you changed the right line, because driver and passenger sides use different parameters by model year and editing the wrong one produces no visible effect. Second, remember that on the passenger side the iDrive generation determines which line applies. Third, the belt warning lamp in the cluster is independent of this coding and continues to illuminate.