Cruise Control (FGR)

Cruise control (FGR)
The cruise control uses the speed signal V1 of the CAN message from the DSC control unit as the control variable and calculates the required cylinder charging. The cruise control (FGR) is activated in different ways in the E31 and E38 (provided there are no switch-off conditions or switch-on inhibits):
- On E31 vehicles via operating lever (steering column switch LSS)
- On E38 vehicles via a main switch on the instrument panel and via the right-hand button pad in the multifunction steering wheel (MFL)

Data Transfer and FGR Operation in E31 Vehicles
In E31 vehicles data is transferred from the operating lever to the EMLIIIS control unit as in the previous EML system by means of resistor coding and the resulting analog voltage.

The following functions are possible, however, the steering column switch (LSS) is designed in such a way that several functions cannot be active simultaneously:
- Lever in rest position: Rest (voltage value 3.33 to 3.55 V)
- Lever forward: Set/accelerate (voltage value 0.76 to 0.91 V)
- Lever back: Decelerate (voltage value 2.49 to 2.75 V)
- Lever up: OFF (voltage value 4.13 to 4.27 V)
- Lever down: OFF (voltage value 4.13 to 4.27 V)
- Press lever: Resume (voltage value 1.57 to 1.80 V)

Data Transfer and FGR Operation in E38 Vehicles
In E38 vehicles, data is transferred from the multifunction steering wheel (MFL) to
the EMLIIIS control unit via digital signals. There is no mechanical interlock between the buttons on the multifunction steering wheel (MFL) to prevent simultaneous operation of several functions so that the functions are recognized in accordance with a priority table with "OFF" having the highest priority.

In order to avoid malfunctions on the multifunction steering wheel, the driver must first switch on the cruise control (FGR) via the FGR main switch on the instrument panel (FGR ready indicator in instrument cluster lights up). The following functions are then possible:
- Buttons not operated: Rest
- Button "+" pressed: Set/accelerate
- Button "-" pressed: Decelerate
- Button "0" pressed: OFF
- Button "pointer" pressed: Resume

Switch-On Inhibits and Switch-Off Conditions
There are various switch-on inhibits and switch-off conditions in both vehicles.

Switch-on inhibits include CAN-bus faults in the DSC message or faults in the brake switch.

Cruise control (FGR) operation can be switched off soft or hard by the EMLIIIS control unit:
- Soft shut-down takes place when the "OFF" function is operated or when the travelling speed is too low
- Hard shut-down takes place when the brake is operated, at excessively high acceleration or excessively high travelling speed, if a gear is no longer engaged in the automatic transmission or in the case of certain defects detected by the self- diagnosis function in the EMLIIIS system.