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

ENGINE 156, 273, 275 in MODEL 216 as of Model Year 09 /AEJ 08 with CODE (219) Distronic (DTR)

ENGINE 156, 272, 273, 275, 642, 629 in MODEL 221 as of Model Year 09 /AEJ 08 with CODE (219) Distronic (DTR)

Fig 1: Detecting Vehicle Traveling Ahead With Distronic Activated

Courtesy of MERCEDES-BENZ USA

Detection of a vehicle traveling ahead with DISTRONIC activated

DISTRONIC function requirements in general

"Circuit 61 ON" (engine running)
"ADTR" (Advanced Distronic) coded in the central gateway control unit (N93)
Dirt and function test of the DTR radar sensor (A89b1) completed successfully
Electronic Stability Program (ESP) not deactivated
Parking brake not applied
Gear range "D" engaged
Brake pedal not actuated
Speed of the vehicle >30 km/h
CC push button (S40/4) pressed to Distronic position (LIM indicator lamp (LIM ITER) off)

DISTRONIC in general

DISTRONIC regulates the speed and the distance to the vehicle driving ahead according to the driver's specifications (target speed and required distance) in the range of 30 to 180 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 preceding vehicle, the speed is reduced in order to maintain the target distance set by the driver by:

Reducing the engine output
Activating the brakes
Shifting gear (downshift)

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.

The DTR control unit (A89n1) actuates the radar sensor, evaluates the data from the DTR radar sensor (A89b1)then transmits this data over the vehicle dynamics CAN (CAN H) 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. To do this, it sends the corresponding CAN signals to the CDI control unit (N3/9) or ME-SFI control unit (N3/10) for acceleration/deceleration) over the chassis CAN, and to the ETC control unit (N15/3) or electric controller unit (VGS) (Y3/8) (to shift gear) over the chassis CAN and drive train CAN (CAN C).

The ESP control unit also actuates warning tones and displays in the instrument cluster (A1).

DISTRONIC function sequence

The function sequence is described in the following points:

Function sequence of soiling and function test
Automatic acceleration function sequence
Automatic braking function sequence
Distronic activation function sequence
Specified speed function sequence
Specified speed function sequence
Special driving situations function sequence
Distronic deactivation function sequence

Function sequence of soiling and function test

The DTR control unit performs a dirt and function test of the radar sensor to ensure smooth functioning of the radar system after each engine start. If a malfunction is found or if there are no objects within the radar detection range of the radar sensor (for the function test), the Distronic can not be activated and the message "Distronic Unavailable" appears on the multifunction display (A1p13) of the instrument cluster.

Automatic acceleration function sequence

For reasons of safety and comfort, automatic acceleration with the Distronic is limited to about 1 m/s² .

Automatic braking function sequence

Intervention by the brake system is limited to 20% (about 2 m/s² ) of the maximum possible deceleration, for reasons of safety and comfort. Driving situations that require more than 20 % braking power are indicated to the driver visually, by the DTR warning and indicator lamp (A1e59) being lit red on the instrument cluster, and audibly through an intermittent warning tone. This intermittent warning tone signals the driver to observe the traffic situation and to intervene if necessary, or reassume full control of the vehicle.

The intermittent warning tone is turned off automatically when the situation becomes less critical and cannot be deactivated manually.

Distronic activation function sequence

The Distronic can be activated at speeds between 30 an 180 km/ h.

By moving the CC [TPM] switch up or down, DISTRONIC is activated with the current vehicle speed as the target speed.

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.

The message "Distronic Unavailable" is displayed if:

The radar plate in the radiator grille is dirty or iced up
Radar operation is not possible due to weather conditions
Transmission/reception signals are limited by external factors (e.g. electromagnetic interference)

Specified speed function sequence

The minimum target speed that can be set is 30 km/h and the maximum target speed 180 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).

View of instrument cluster with 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.

Specified speed function sequence

With the DTR distance potentiometer (N72r1), the specified distance from the vehicle in front can be set in six steps between about 1.0 and 2.0 s, depending on vehicle speed.

At setting three and at a speed of 100 km/h, this corresponds to a target distance of around 42 m. The specified distance is converted from seconds to meters (depending on the driver's own vehicle speed), and displayed in the form of a line on the multifunction display of 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.

If the set target speed to the vehicle ahead falls short, DISTRONIC reduces the speed.

In driving situations requiring more than 20 % braking power, the DTR warning and indicator lamp in the instrument cluster are lit and the intermittent warning tone signals the driver to watch the traffic situation so that he can intervene by measured heavy braking or by steering if necessary.

View of instrument cluster when the vehicle is below the specified distance

Fig 3: View Of Instrument Cluster When Vehicle Ahead 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 function sequence

If the driver accelerates the vehicle independently higher than the acceleration set by DISTRONIC or accelerates up to over 180 km/h, DISTRONIC is not deactivated, but switches to passive. The multifunction display on the instrument cluster displays the message "Distronic passive" and no distance control from the vehicle in front is performed during this acceleration. When the driver releases the accelerator pedal again (vehicle speed drops), DISTRONIC resets to the set target speed and distance control is once again activated.
No regulation takes place relative to stationary objects.
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 case of any obstacle in the way, the DTR warning and indicator lamp and the intermittent warning tone signal any impending collision.

Distronic deactivation function sequence

DISTRONIC is deactivated when:

The CC [TPM] switch is pushed forwards
The brake pedal is operated.
CC [TPM] push button pressed to Variable Speed Limiter position (LIM indicator lamp is lit)
Gear range "N" is engaged
A vehicle in front moving at a speed of <30 km/h is no longer detected (lost)
Radar function no longer available

Electrical function schematic for Distronic (DTR)	Model 216	PE30.30-P-2050-97CAB
Electrical function schematic for Distronic (DTR)	Model 221	PE30.30-P-2050-97SAD
DTR controller unit, component description	A89	GF30.30-P-3210LEA
ESP control unit, component description	N47-5	GF42.45-P-5118LE