Blind Spot Assist, Function - GF54.71-P-0003FH
Model 238
Up To Model Year 2021
with code 22P (Lane tracking package)
Model 238
Up To Model Year 2021
with code 234 (Blind Spot Assist)
Function requirements, general
- No undervoltage or overvoltage
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed: Over 10 km/h
- No trailer operation (with code 550 (Trailer hitch))
Blind Spot Assist, general
The Blind Spot Assist monitors the rear and side areas of the vehicle using short range radar and, if necessary, informs the driver that an intentional lane change (turn signal active) is not recommended at this time. In a broader sense, Blind Spot Assist serves as an extension of the outside mirror. On no account is the driver released from his obligation to make the lane change safely.
The Blind Spot Assist is activated via the head unit. The following options are available for navigating in the control menu:
- Except code 446 (Touchpad only), navigation can be performed using the Audio/COMAND control panel. The corresponding control signals are sent by the Audio/COMAND control panel (except code 446 (Touchpad only)) over the telematics CAN to the head unit.
- With code 446 (Touchpad only) or code 448 (Touchpad), navigation can be performed using the touchpad. The corresponding control signals are sent by the touchpad (with code 446 (Touchpad only) or code 448 (Touchpad)) over the telematics CAN to the head unit.
- Navigation can be operated by voice control with code 531 (COMAND APS). The driver hands-free system microphone sends the signals directly to the head unit.
- Navigation can be performed via the head unit finger navigation pad and the "Back" button on the steering wheel. The corresponding operation signals are sent by the head unit finger navigation pad and the "Back" button over the steering wheel electronics, steering LIN (up to model year 2019) or the steering wheel CAN (as of model year 2019), steering column tube module control unit, suspension FlexRay, electronic ignition lock control unit and the user interface CAN to the head unit.
- With code 246 (Analog clock), the control menu can be called up with the Vehicle button in the upper control panel control unit. The status of the Vehicle button is sent by the upper control panel control unit over the LCP-LIN, the Audio/COMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)) and the telematics CAN to the head unit.
The head unit sends the status of the Blind Spot Assist via the user interface CAN, electronic ignition lock control unit and periphery CAN to the rear bumper integrated radar sensors.
The visual warning output takes place via the following components:
- Left blind spot assistant warning indicator
- Right blind spot assistant warning indicator
The acoustic warning is output via the instrument cluster speaker; the readiness indicator is displayed in the instrument cluster.
The area which cannot be observed via the outside mirror and inside rear-view mirror is monitored by the following components:
- Right outer rear bumper integrated radar sensor
- Left outer rear bumper integrated radar sensor
All relevant data is evaluated by the integrated rear bumper radar sensors, whereby the right rear bumper radar sensor requests the warning output.
The integrated rear bumper radar sensors operate according to the "Master-slave" principle. The master or slave function can be determined via the connector coding. The master function is defined for the integrated right rear bumper radar sensor. In other words, the integrated left rear bumper radar sensor sends its information via the periphery CAN to the integrated right rear bumper radar sensor which evaluates the corresponding information from both integrated rear bumper radar sensors and sends corresponding requests or data over the periphery CAN to the corresponding control units.
Illustration of Blind Spot Assist principle, shown on model 238.3
The following information is evaluated by the radar sensors integrated in rear bumper:
- Terminal status of terminal 15
- "Blind Spot Assist" status
- Engine running or drive train operational
- Vehicle in forward movement, vehicle speed
- Steering wheel angle
- Trailer operation status (with code 550 (Trailer hitch))
Status of circuit 15:
The electronic ignition lock control unit sends the status of circuit 15 via the periphery CAN to the radar sensors integrated in the rear bumper.
"Blind Spot Assist" status:
The head unit sends the status of the Blind Spot Assist via the user interface CAN, electronic ignition lock control unit and periphery CAN to the rear bumper integrated radar sensors.
Engine running or drive train operational:
The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal via the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and periphery CAN to the radar sensors integrated in the rear bumper.
Vehicle in forward movement, vehicle speed:
Forward movement is defined via the wheel rotation direction. The vehicle speed is calculated from the wheel speed. The Electronic Stability Program control unit sends this information via the suspension FlexRay, electronic ignition lock control unit and periphery CAN to the rear bumper integrated radar sensors. The rear bumper integrated radar sensors use it to calculate the vehicle speed and the direction of travel.
Steering wheel angle:
The steering wheel angle sensor detects/records the steering wheel angle. The steering column tube module control unit reads in the signals of the steering wheel angle sensor directly and sends information on the steering wheel angle via the suspension FlexRay, electronic ignition lock control unit and periphery CAN to the rear bumper integrated radar sensors.
Trailer recognition (with code 550 (Trailer hitch)):
When the trailer recognition control unit has detected a trailer, it sends the "Trailer detected" status to the integrated rear bumper radar sensors over the interior CAN, electronic ignition lock control unit and periphery CAN.
The Blind Spot Assist system includes the following subfunctions:
- Measuring method
- System and warning messages
Measuring method
Objects (vehicle in blind spot) are detected using the radar measuring procedure. The radar sensors integrated in the rear bumper emit bundled electromagnetic waves as "primary signals". If these waves hit an object, they are reflected by it and are received again by the corresponding radar sensor integrated in the rear bumper as a secondary signal. These signals are used to calculate the distance and the speed of the detected object as well as its angle relative to the vehicle.
Detection range of radar sensor system, shown on model 238.3
The integrated rear bumper radar sensors detection range is based on the angles of the radar waves. These are extrapolated by the respective integrated rear bumper radar sensor to produce the actual monitoring ranges.
System and warning messages
When circuit 15 is switched on, the Blind Spot Assist warning indicators light up in red, until the CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train operational" signal. Additionally, when the "Assistance" menu is switched on in the instrument cluster, the readiness of the Blind Spot Assist is shown in the instrument cluster.
If system errors are detected, a corresponding message is shown in the instrument cluster.
The function readiness status and/or the request to output fault messages is sent by the right rear bumper radar sensor via the periphery CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster (output of fault messages) and via the periphery CAN, electronic ignition lock control unit and interior CAN to the respective front door control unit, which then actuates the corresponding Blind Spot Assist warning indicator.
If, at a speed of more than 8 a vehicle is located in the acquisition range of the radar sensor system, the driver is warned by the Blind Spot Assist warning indicator lighting up red in the outside mirror, on the side on which the vehicle is in the blind spot. Regardless of their speed differential to the vehicle, passing vehicles are recognized and a warning is issued with Blind Spot Assist. Due to the short reaction time when the difference in speed is high, the warning message output sometimes does not have any added value. If, despite illumination of the Blind Spot Assist warning indicator, the driver still attempts to change lane and indicates this by operating the combination switch (turn signal active), a dual warning tone is additionally output via the instrument cluster speaker, which is actuated directly by the instrument cluster. The Blind Spot Assist warning indicator flashes on and off. If the vehicle leaves the detection range of the radar sensor system, the red flashing Blind Spot Assist warning indicator is switched off.
The steering column tube module control unit directly reads in the switch position of the combination switch and sends it to the integrated rear bumper radar sensors over the chassis FlexRay, electronic ignition lock control unit and periphery CAN.
Blind Spot Assist warning indicator, shown on left outside mirror
The following table contains the requirements for displaying system readiness and for showing the visual warning messages:
| Operating state | Blind Spot Assist warning indication in the outside mirror "Off" | Blind Spot Assist readiness indicator in the instrument cluster, function status "On" | Blind Spot Assist readiness indicator in the instrument cluster, function status "Operational" | Blind Spot Assist warning indication in the outside mirror, red on | Blind Spot Assist warning indication in the outside mirror, flashing red |
|---|---|---|---|---|---|
| Circuit 15 OFF | On | - | - | - | - |
| Terminal 15 ON | - | - | - | On | - |
| Engine running or drive train operational | On | - | - | - | - |
| Active Blind Spot Assist activated via the instrument cluster | - | On | - | - | - |
| Vehicle accelerates, vehicle speed above 8 km/h | On | - | On | - | - |
| Vehicle decelerates, vehicle speed below 25 km/h | On | On | - | - | - |
| Trailer recognized (with code 550 (Trailer hitch)) | On | - | - | - | - |
| Gear range "R" (transmission 725) or reverse gear (with transmission 716) engaged | On | On | - | - | - |
| Vehicle recognized in blind spot | - | - | On | On | - |
| Turn signal active, vehicle detected in blind spot | - | - | On | - | On |
| Fault detected | On | - | - | - | - |
Gear range "R" engaged (transmission 725):
Gear range "R" is engaged through the fully integrated transmission control unit. The fully integrated transmission control unit then sends the "Gear range R engaged" status to the electronic ignition lock control unit over the drive train CAN, powertrain control unit and suspension FlexRay. The electronic ignition lock control unit generates a "Reverse gear engaged" status and sends this over the periphery CAN to the integrated rear bumper radar sensors.
Reverse gear engaged (transmission 716):
Engaging the reverse gear is recorded by the manual transmission main shifter shaft position sensor. The powertrain control unit reads in the signals from the manual transmission main shifter shaft position sensor directly, uses them to generate the "reverse gear engaged" signal and sends this signal via the suspension FlexRay to the electronic ignition lock control unit. The electronic ignition lock control unit generates the "Reverse gear engaged" status and sends it via the periphery CAN to the radar sensors integrated in the rear bumper.
| Electrical function schematic, blind spot assistant | PE54.71-P-2051-97DCA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998FH |