Blind Spot Assist, Function - GF54.71-P-0003RF
Model 205
up to model year 2019
with code 234 (Blind Spot Monitoring)
Model 253 (except 253.99)
up to model year 2020
with code 234 (Blind Spot Monitoring)
Function requirements, general
- No undervoltage or overvoltage
- Blind Spot Assist in "Assistance" activated in instrument cluster
- Engine running or drive train operational.
- Vehicle moving forward
- Vehicle speed: v ≥ 30 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 also acts as an extension of the outside mirrors and the inside rearview mirror. It does not release the driver of his/her obligation to perform lane changes safely on his/her own responsibility.
In the respective outside mirror, a visual indicator warns of critical situations during a lane change (i.e. a vehicle is in the blind spot). A warning tone can also be issued.
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 are evaluated by the rear bumper radar sensors, whereby the right rear bumper radar sensor requests the warning output.
The 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 right rear bumper radar sensor. In other words, the left rear bumper radar sensor sends its information over the periphery CAN to the right rear bumper radar sensor which then evaluates the corresponding information from both rear bumper radar sensors and sends corresponding requests or data over the periphery CAN to the corresponding control units.
Illustration of the principle of Blind Spot Assist, shown on model 205.0
The following information is evaluated by the rear bumper radar sensors:
- Terminal status of terminal 15
- "Blind Spot Assist" status
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed
- Status of trailer recognition (with CODE 550 (Trailer hitch))
Status of circuit 15:
The electronic ignition lock control unit sends the status of circuit 15 over the periphery CAN to the rear bumper radar sensors. "Blind Spot Assist" status:
The status of the Blind Spot Assist is sent by the instrument cluster to the integrated rear bumper radar sensors over the user interface CAN, electronic ignition lock control unit and periphery CAN.
Engine running or drive train operational:
The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drive train operational" signal to the rear bumper radar sensors over the drive train CAN, drivetrain control unit, chassis FlexRay, electronic ignition lock control unit and the periphery CAN.
Vehicle moving forward:
Forward movement is defined via the wheel rotation direction. The Electronic Stability Program control unit transmits the information about the wheel rotation direction over the chassis FlexRay, electronic ignition lock control unit and periphery CAN to the rear bumper radar sensors. Vehicle speed:
The vehicle speed is calculated from the wheel speed. The Electronic Stability Program control unit sends the information on wheel speed over the chassis FlexRay, electronic ignition lock control unit and the periphery CAN to the rear bumper 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 rear bumper radar sensors over the interior CAN, electronic ignition lock control unit and the periphery CAN. The Blind Spot Assist system includes the following subfunctions:
- Measuring procedure function sequence
- Function sequence for system and warning messages
Measuring procedure function sequence
Objects (vehicle in blind spot) are detected using the radar measuring procedure. The rear bumper radar sensors 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 rear bumper radar sensor 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 area of the radar sensor system, shown on model 205.0
The detection range of the rear bumper radar sensors is based on the angle of reflection of the radar waves. These are extrapolated by the respective rear bumper radar sensor to produce the actual monitoring ranges.
Illustration showing the actual rear monitoring range, shown on model 205.0
Function sequence for system and warning messages
When circuit 15 is switched on, the Blind Spot Assist readiness and warning indicators light up 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, the readiness of the Active Blind Spot Assist is shown in the instrument cluster's multifunction display (gray radar waves appear spreading towards the rear next to the vehicle). If system errors are detected, a corresponding fault message appears instead of the readiness indicator. The right rear bumper radar sensor sends the request t o issue system, fault and warning messages over the periphery CAN, electronic ignition lock control unit and the user-interface CAN to the instrument cluster (issue of fault messages) and over the periphery CAN, electronic ignition lock control unit and the interior CAN to the respective front door control unit, which then actuates the corresponding Blind Spot Assist readiness and warning indicator.
If a vehicle is in the detection range of the radar sensor system at a vehicle speed of v ≥ 30 km/h, the driver is warned by the Blind Spot Assist readiness and warning display illuminating in the outside mirror on the side in which the vehicle is in the blind spot. Additionally, a warning is shown in the multifunction display of the instrument cluster. 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 readiness and warning lamp, the driver still attempts to change lane and indicates this by operating the combination switch (turn signal active), a double warning tone is additionally issued once by the instrument cluster speaker. The Blind Spot Assist readiness and warning indicator flashes on and off. If the vehicle leaves the radar sensor system's sensing range, the red flashing Blind Spot Assist readiness and 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 rear bumper radar sensors over the chassis FlexRay, electronic ignition lock control unit and periphery CAN.
The instrument cluster directly actuates the external instrument cluster speaker in order to output the double acoustic warning.
Blind Spot Assist readiness indicator
The function status "OFF" display is issued when the Blind Spot Assist is deactivated and in a fault instance.
When the Blind Spot Assist is switched on through the "Assistance" menu in the instrument cluster, an "ON" function status is displayed. The Blind Spot Assist is activated but not ready to issue warnings, as additional function requirements such as a vehicle speed of v ≥ 30 km/h are not given. When the function status "Operational" is issued by instrument cluster, the Blind Spot Assist is switched on and all additional function requirements are met. The Blind Spot Assist is ready to issue a warning.
Blind Spot Assist warning indication (in the outside mirror), 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 | X | ||||
| Terminal 15 ON | X | ||||
| Engine running or drive train operational | X | ||||
| Blind Spot Assist activated through instrument cluster | X | ||||
| Vehicle accelerates, vehicle speed v ≥ 30 km/h | X | X | |||
| Vehicle decelerates, vehicle speed v ≥ 25 km/h | X | X | |||
| Trailer recognized (with code 550 (Trailer hitch)) | X | ||||
| "R" drive range (transmission 722, 724, 725) or reverse gear engaged (transmission 716) | X | X | |||
| Vehicle recognized in blind spot | X | X | |||
| Turn signal active, vehicle detected in blind spot | X | X | |||
| Fault detected | X |
Model 205 with transmission 722, 724, 725
up to model year 2019
with code 234 (Blind Spot Monitoring)
Model 253 (except 253.99) with transmission 724, 725
up to model year 2020
with code 234 (Blind Spot Monitoring)
Gear range "R" engaged:
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, drivetrain 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 rear bumper radar sensors.
Model 205 with transmission 716
up to model year 2019
with code 234 (Blind Spot Monitoring)
Model 253 (except 253.99) with transmission 716
up to model year 2020
with code 234 (Blind Spot Monitoring)
Reverse gear engaged:
Engaging the reverse gear is recorded by the manual transmission main shifter shaft position sensor. The CDI control unit or the ME-SFI [ME] control unit reads in the signals of the manual transmission main shifter shaft position sensor directly, uses it to generate the "Reverse gear engaged" signal and sends this to the electronic ignition lock control unit over the drive train CAN, the drivetrain control unit and the chassis FlexRay. The electronic ignition lock control unit generates a "Reverse gear engaged" status and sends this over the periphery CAN to the rear bumper radar sensors.
| Electrical function schematic, blind spot assistant | PE54.71-P-2051-97FBA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998RF |