(Component Description For Intelligent Radar Sensor Control Unit - GF30.30-P-3305RD)

Model 172.4 

as of model year 2013 up to model year 2016 

with code 234 (Blind Spot Monitoring) 

Shown on a removed rear bumper 

Courtesy of MERCEDES-BENZ USA

Location 

The bumper radar sensors at the rear are mounted on the left and right on the inner side of the rear bumper.

Tasks 

The rear bumper radar sensors detect vehicles in the blind spot over the integrated vehicles radar sensor system.

The rear bumper radar sensors are ultra wideband radar sensor with the following properties:

• Detection range s = 0.18 to 3 m at a resolution of s = 0.04 m
• Detection angle of ∠ = 60° with angle measurement and ∠ = 130° detection only
• Carrier frequency f = 24.125 GHz
• Method of operation: short pulse method with f = 5 GHz band width

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 requests to output warning and readiness messages via the front end CAN (CAN G) to the right rear bumper radar sensor which then evaluates the information from both radar sensors and, forwards appropriate requests via the front end CAN to the respective control units. Coding (differentiation) for the radar sensors takes place by means of different assignment with ground on pin 5 and 6.

The rear bumper radar sensors also fulfill the following tasks:

• Reading in sensors and signals 
• Evaluation of input factors 
• Output of signals 

Reading in sensors and signals 

The following input factors are read in via the front end CAN:

• Terminal status of terminal 15
• Combination switch position (S4)
• Status of "Blind Spot Assist" function (from the IC (A1)
• Position data from navigation (for the Western Europe version)
• Gear range engaged
• Signal "Engine running" or "Drivetrain operational"
• Wheel speeds and wheel rotation direction

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

Evaluation of input factors 

The input factors are evaluated by the integrated microprocessors and the relevant assembly parts are then actuated.

Output of signals 

Output of signals takes place via the front end CAN.

The right rear bumper radar sensor transmits the following signals via the front end CAN:

• Request to issue acoustic warnings
• Request to issue system or warning messages

The left rear bumper radar sensor transmits detection data to the right rear bumper radar sensor via the front end CAN which uses it to generate the requests to emit a warning.