Steering Column Tube Module Control Unit (MRM), Component Description - GF54.21-S-6052TRA

Model 447.6/7/8

Except Code XM7 (MOPF II)

Model 448.7/8

Steering wheel uninstalled, shown on model 447.8

Fig 1: Steering Column Tube Module Control Unit (MRM) Components Location - Model 447.6/7/8 Except Code XM7 (Shown On Model 447.8)

Courtesy of MERCEDES-BENZ USA

Location

The steering column tube module (MRM) control unit is located directly behind the steering wheel or the multifunction steering wheel (MFL) (with CODE CL4 (Multifunction steering wheel with trip computer)) on the steering column tube of the steering column.

Task

The steering column tube module (MRM) control unit has the following tasks:

Reading in of sensors and signals
Evaluation of input parameters
Actuation of component parts
Sending signals

Reading in of sensors and signals

The input parameters are read in over the following connections:

Direct line
Steering LIN (LIN E1)
Suspension CAN (CAN E)

Direct line

The signals from the following component parts are read in over a direct line:

Steering wheel angle sensor
Combination switch
DIRECT SELECT lever (with transmission 722.9)
Cruise control lever (with CODE MS1 (Cruise control) and with or without CODE ET4 (DISTRONIC PLUS))
- Resume from memory switch
- Decelerate and set switch
- Accelerate and set switch
- OFF switch
- SPEEDTRONIC switch
- SPEEDTRONIC LED
- DISTRONIC controller (with CODE ET4 (DISTRONIC PLUS)) (model 447.8 or model 448.8)

Steering LIN

The following signals that have been read in by steering wheel electronics (N135) are read in over the steering LIN:

Left multifunction steering wheel button group (S110) (with CODE CL4 (Multifunction steering wheel with trip computer))
Right multifunction steering wheel button group (S111) (with CODE CL4 (Multifunction steering wheel with trip computer))
Steering wheel downshift button (S110/1) (with CODE G42 (7G-TRONIC PLUS))
Steering wheel upshift button (S111/1) (with CODE G42 (7G-TRONIC PLUS))

Suspension CAN

The steering column tube module (MRM) control unit reads in, for example, the following signals over the suspension CAN:

Terminal status, tml. 15
Terminal status, tml. 58d (Search lighting)
Request to actuate steering wheel vibration motor (M99) (with CODE JW5 (Lane Keeping Assist))

The functions that use these signals are described in the individual function descriptions (see block diagram or function schematic).

Evaluation of input parameters

The input parameters that have been read in are evaluated by the integrated microprocessor and the relevant component parts are then actuated.

Actuation of component parts

Component parts are actuated with the following line:

Steering LIN
Direct line

Steering LIN

The following signals are sent over the steering LIN for steering wheel electronics:

Symbol lighting, for actuation by:
- Left multifunction steering wheel button group (with CODE CL4 (Multifunction steering wheel with trip computer))
- Right multifunction steering wheel button group (with CODE CL4 (Multifunction steering wheel with trip computer))
Actuation of steering wheel vibration motor (with CODE JW5 (Lane Keeping Assist))

Direct line

The signals from the Supplemental Restraint System (SRS) control unit (N2/18) for actuation of the driver's airbagndpille 1 (R12/7r1) and the driver's airbagndpille 2 (R12/7r2) are looped over a direct line by the steering column tube module (MRM) control unit.

The SPEEDTRONIC LED (with CODE MS1 (Cruise control)) is actuated over a direct line.

Sending signals

The steering column tube module (MRM) control unit sends, for example, the following signals over the suspension CAN:

Steering wheel angle, steering wheel velocity
Left multifunction steering wheel button group (with CODE CL4 (Multifunction steering wheel with trip computer))
Right multifunction steering wheel button group (with CODE CL4 (Multifunction steering wheel with trip computer))
Combination switch, status
Status of DIRECT SELECT lever (with transmission 722.9)
Cruise control lever status (with CODE MS1 (Cruise control) and with or without CODE ET4 (DISTRONIC PLUS))

The functions that use these signals are described in the individual function descriptions (see block diagram or function schematic).

Wiring diagram for steering column tube module control unit	Model 448	PE46.10-S-2101-97VDA
	Model 447.8 except code XM7 (MOPF II)	PE46.10-S-2101-97VVA
	Model 447.6/7 except code XM7 (MOPF II)	PE46.10-S-2101-97VVB