DISTRONIC, function - GF30.30-P-3200SX

ENGINE 272 in MODEL 221 with CODE (219) Distronic (DTR) up to Model Year 8

ENGINE 273 in MODEL 221 with CODE (219) Distronic (DTR) up to Model Year 8

Fig 1: Detecting Vehicle Travelling Ahead With Distronic System

Courtesy of MERCEDES-BENZ USA

Detection of a vehicle traveling ahead with DISTRONIC activated

DISTRONIC regulates the speed and the distance from the vehicle ahead according to specification by the driver (target speed and target distance) within the range from 30 km/h to 200 km/h.

In doing so, DISTRONIC regulates the set target speed in an empty lane (no vehicle moving ahead) as per conventional cruise control. As the car approaches a vehicle moving ahead, the speed is reduced in order to maintain the target distance set by the driver by:

Reducing the engine output
Activating the brakes
Shifting the gear

If the traffic situation allows an increase in speed as the vehicle immediately ahead has accelerated or left the lane, for example, Distronic increases the speed back up to the set target speed.

Function requirements

"Circuit 61 ON" (engine running)
ESP not deactivated
Parking brake not operated
DIRECT SELECT gear selector switch (S16/13) in "D" position
By pressing the CC [TPM] switch (S40/4) a switchover to the DISTRONIC position must take place (LIM indicator lamp off)
Dirt/function test of DTR radar sensor (A89b1) completed successfully
DISTRONIC coded in Central Gateway control unit (N93)

Dirt/function test

To guaranteed the smooth function of the radar system after each engine start, the DTR control unit (A89n1) performs a dirt/function test of the radar sensor. If a malfunction is established or no objects (for the function test) are available in the radar sensor detection range, DISTRONIC cannot be activated and the message 'DISTRONIC not available appears in the multifunction display (A1p13) of the instrument cluster (A1).

The DTR control unit actuates the radar sensor, evaluates the radar sensor data and then transmits this data via the drive dynamic CAN to the ESP control unit (N47-5).

Following evaluation of all sensor data and input signals, the ESP control unit takes over control of the entire longitudinal movement of the vehicle in DISTRONIC operation. For this purpose, it sends signals (for shifting gear, accelerating or decelerating) via the chassis CAN to the corresponding control units.

The ESP control unit also actuates warning chimes and displays in the instrument cluster.

Automatic acceleration

The automatic maximum acceleration by DISTRONIC is limited to around 2.5 m/s² for reasons of safety and comfort.

Automatic braking

Intervention by the brake system is restricted to 40% (approx. 4 m/s² ) of the maximum possible deceleration capacity for reasons of safety and comfort. Driving situations requiring more than 40% braking power are indicated to the driver visually by the DTR warning lamp (A1e59) in the instrument cluster and acoustically by a tone. This takeover tone is an intermittent tone and signals to the driver to observe the traffic situation carefully and to intervene if necessary and to reassume full control of the vehicle. The takeover tone is shut off automatically when the situation becomes less critical; it cannot be deactivated manually.

Target speed

The minimum target speed that can be set is 30 km/h and the maximum target speed 200 km/h.

The CC [TPM] switch can be moved up or down (S40/4) to increase or decrease the target speed in 1 km/h or 10 km/h increments (two settings).

Activation

DISTRONIC can be activated from 30 km/h up to a speed of 260 km/h. Here, when DISTRONIC is activated the target speed between 200 km/h and 260 km/h, the target speed is set automatically to the maximum permissible target speed of 200 km/h.

Pulling or moving the CC [TPM] switch up or down will activate DISTRONIC

By pulling the CC [TPM] switch, DISTRONIC is activated with the last saved target speed provided that a target speed has already been saved since the last engine start (set). If no target speed is stored, the current vehicle speed is set as the target speed.
By moving the CC [TPM] switch up or down, DISTRONIC is activated with the current vehicle speed as the target speed.

The message "DISTRONIC not available" is displayed, for example, when the radar plate in the radiator grill is soiled or iced up, operation is not possible due to weathering or the transmitter/ receiver signals are restricted by external influences (e.g. EMC interference).

DISTRONIC activated

Fig 2: View Of Instrument Cluster With Distronic Activated

Courtesy of MERCEDES-BENZ USA

The orange triangle at the top of the segment ring indicates the set target speed. In the Electronic Speedometer (A1p8) of the instrument cluster, when DISTRONIC is activated, the segments between the measured speed of the vehicle moving ahead and the set target speed are illuminated.

The vehicle ahead is shown with the actual distance in meters.

Target distance

Using the DTR distance potentiometer (S40/4r1), which is integrated in the CC [TPM] switch, the target distance to the vehicle ahead can be set in six increments between approx. 1.0 s and 2.0 s depending on the speed. At setting three and at a speed of 100 km/h, this corresponds to a target distance of around 42 m.

The target distance is converted from seconds to meters depending on the speed of the host vehicle, and is displayed in the form of a white line on the range indicator in the instrument cluster.

The target distance in the distance indicator matches the current vehicle speed without the driver having to adjust the DTR distance potentiometer.

The legally required minimum distance is thus always guaranteed in the setting range for the target distance.

Target distance falls short

Fig 3: View Of Instrument Cluster When Target Distance Falls Short

Courtesy of MERCEDES-BENZ USA

If the set target speed to the vehicle ahead falls short, DISTRONIC reduces the speed. In driving situations requiring more than 40 % braking power, the DTR warning lamp in the instrument cluster is lit and the takeover tone signals to the driver to carefully observe driving situation and to intervene himself by measured heavy braking or steering if necessary.

Special driving situations

If the driver accelerates the vehicle independently higher than the acceleration set by DISTRONIC or accelerates up to over 200 km/h, DISTRONIC is not deactivated, but switches to passive. In the multifunction display of the instrument cluster, the message "DISTRONIC passive" appears and distance control from the vehicle ahead does not take place for this acceleration procedure.
If the driver once more releases the accelerator (vehicle speed decreases), DISTRONIC once again regulates the set target speed and distance control is reactivated.
Control does not take place for stationary targets.
If a vehicle cuts in between the host vehicle and the vehicle ahead (target vehicle), the system switches over to the new target vehicle.
If, during the journey, the vehicle ahead pulls out of the lane and another vehicle is now moving ahead of the host vehicle, then the system will only control the distance to this new vehicle if it is moving. In the event that a stationary obstruction is encountered, an intermittent takeover tone and the DTR warning lamp warn the driver about the impending collision.

Deactivation

DISTRONIC is deactivated when:

The CC [TPM] switch is pushed in
The brake pedal is operated.
By pressing the CC [TPM] switch, a switchover to the Variable Speed Limiter takes place (LIM indicator lamp lights up)
DIRECT SELECT gear selector switch in position "N"
Vehicle moving at a speed of <30 km/h is "lost"
Function requirements for the DISTRONIC function are no longer provided

	CC [TPM] switch, component description	S40/4	GF30.20-P-2100UX
	DTR control unit, component description	A89	GF30.30-P-3210TX