Drive control (FR) function

W30.35-1177-09

A3 Drive control (FR) control unit

A4 Flame starting system control unit (FLA)

A6 Engine control (MR) control unit

A42 Immobilizer read-out electronics

B1 Foot throttle actuator

B2 Clutch travel sensor

B3 Countershaft rpm sensor

B4 Outside temperature sensor

B6 Coolant level switch

B7 Air filter monitoring sensor

CAN 1 Vehicle CAN

CAN 4 Engine CAN

G2 Alternator

Y1 Pneumatic constant throttle solenoid valve (4-cylinder engines)

Y2 Engine brake flap solenoid valve

Y29 Splitter 1 solenoid valve (MS1)

Y30 Splitter 2 solenoid valve (MS2)

Y49 Hydraulic constant throttle solenoid valve (6-cylinder engines)

Z1 CAN star point cab dash support

P1 Tachograph

P2 Instrument (INS)

P3 Modular tachograph (MTCO)

P4 Instrument cluster

S2 Operating lever for engine brake/permanent brake

S4 Stop lamp switch

S7 Reverse gear switch

S9 Neutral position switch

S82 Engine start/stop switch (with code (MJ6) Start engine and Stop system)

General information

The drive control unit (FR), like the engine control unit (MR), is an independent, electronic system which provides the interface between the chassis and the drive train. It regulates, controls and monitors all vehicle-specific functions which are required while driving, whereby the main task is to calculate the torque specified and required by the driver from the engine and to transmit this to the engine regulation unit (MR). The central control unit is the drive control (FR) control unit (A3) which is networked via the vehicle CAN (CAN 1) with various equipment including the instrument (INS) (P2) and via engine CAN (CAN 4) with the engine control (MR) control unit (A6).

1 Base functions of the drive control (FR)

1.1 Computation and transfer of the engine specified torque

The specified engine torque is a purely calculated value based on the driving requirements of the driver. This value is primarily dependent on the position of the gas pedal which is determined by the drive control (FR) control unit (A3) in co-operation with the foot throttle actuator (B1).

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 The drive control (FR) control unit (A3) can limit the specified engine torque to maintain the legally prescribed maximum speed or during a regulating intervention of the Antilocking System (ABS) or the Acceleration Slip Regulation (ASR). Once the drive control (FR) has calculated the specified engine torque the specified engine torque is transmitted via the engine CAN (CAN 4) to the engine control (MR) control unit (A6).

1.2 Controlling the constant throttle and engine brake flap

Depending on the engine variant and the vehicle equipment, there is either a pneumatic or an hydraulic constant throttle installed. Actuation of the respective solenoid valves, which either pass on oil or compressed air to the respective constant throttles, takes place either by the drive control (FR) control unit (A3) or the engine control (MR) control unit (A6).

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Controlling of the engine braking flap does, however, always take place via the engine control (MR) control unit (A3)

1.3 Determination and provision of the vehicle speed

The drive control (FR) determines the current vehicle speed based on various input values which a number of factors depend upon, including limitation of the specified engine torque, and makes this available to the other systems via the vehicle CAN bus (1).

1.4 Alternator pre-regulation and monitoring of the charging current

Alternator pre-regulation does not take place via the charging indicator lamp but instead by means of a circuit in the drive control (FR) control unit (A3).

The drive control (FR) control unit (A3) also monitors the charge current of the alternator (G2) and requests indication of the symbol for charge control in the instrument (INS) (P2) via the vehicle CAN bus (1) if the charge current is either too low or missing altogether.

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2 Additional functions of the drive regulation (FR)

2.1 Vehicles with code (MD9 Cruise control)

Speed control for vehicles with code (MD9) Cruise control is integrated as software function in the drive control (FR) control unit (A3) and can be actuated via the operating lever for engine brake/permanent brake (S2).Regulation of the desired vehicle speed is achieved by means of appropriate adjustment of the specified engine torque.

2.2 Vehicles with power take-off

The working speed control with variable or fixed speed is realizable for the power take-off over the drive control (FR).

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2.3 Vehicles with transmission 715.320

On vehicles fitted with transmission 715.320 additional following transmission control functions are available

 Splitter control

 Overspeed warning

 Shift force assist

3 Diagnostic functions of the drive control (FR)

When the drive control (FR) is installed, the majority of installed components are monitored by the drive control (FR) control unit (A3). Components which cannot be monitored (switches etc.) can be checked in full using measurement and binary values. In certain cases, connected components can be measured in test mode (resistance measurement) or a test actuation performed (active test).