LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> BMW >> 2012 >> 335is 2D Coupe >> Repair and Diagnosis >> Restraints >> Restraints Control Systems >> Restraint System - Functional Description - E92 >> Restraints Systems - Functional Description >> Multiple Restraint System (MRS) >> MRS control unit
April 5, 2026: LEMON Manuals is launched! Read the announcement.

MRS control unit

The MRS control unit is bolted in a central position in the vehicle onto the gearbox tunnel. All inflator assemblies and sensors are connected directly to the MRS control unit. The MRS control unit evaluates the data from the sensors. In the event of a collision, the MRS control unit decides whether it is required to trigger the various restraint systems and which ignition circuits have to be triggered.

Two acceleration sensors are fitted in the MRS control unit. The longitudinal acceleration sensor detects frontal or rear-end collisions. The lateral acceleration sensor acceleration sensor detects a side impact.

An ignition capacitor is fitted in the MRS control unit. If the voltage supply is interrupted in a collision, the ignition capacitor serves as an energy reserve for the MRS control unit.

Fig 1: MRS Control Unit Communication Diagram
G09871930Courtesy of BMW OF NORTH AMERICA, INC.
Item Explanation
1 Left knee airbag (US version)
2 Airbag front sensor, driver's side (US version)
3 Telematics Control Unit (TCU)
4 Footwell module (FRM)
5 Instrument panel (KOMBI)
6 Car access system (CAS)
7 Junction Box Electronics (JBE)
8 Switch for front passenger airbag deactivation (European version)
9 Airbag front sensor, front passenger side (US version)
10 Right knee airbag (US version)
11 Front door airbag sensor on front passenger side (US version)
12 Front passenger airbag
13 Side airbag, right
14 Airbag sensor, B-pillar, passenger's side
15 Front passenger seat occupancy detector (Europe version)
16 Front passenger seat occupancy detector (US version)
17 Belt tensioner for front passenger seat belt
18 Reel tensioner for front passenger seat belt (US version)
19 Safety battery terminal
20 Connection to starter motor and alternator
21 Battery
22 Reel tensioner for driver's seat belt (US version)
23 Belt tensioner for driver's seat belt
24 Seat belt buckle switch for front passenger seat belt
25 Belt buckle switch for driver belt
26 Ground point
27 Airbag sensor, B-pillar, driver's side
28 Battery cable monitoring wire
29 Side airbag, left
30 Driver's airbag
31 Steering column switch center (SZL)
32 Front door airbag sensor on driver's side (US version)
33 Indicator lamp for front passenger airbag deactivation
34 MRS control unit (with longitudinal and lateral acceleration sensor)
Instrumentation bus Instrumentation bus
Body bus Body bus
Body CAN Body CAN
Terminal R Terminal R