Electronic Throttle Actuator: Description and Operation

GF30.20-P-3015MMC Electronic Accelerator Function
- ENGINES 157.9 in MODEL 216.3, 221.0 /1
- ENGINES 278.9 in MODEL 216.3, 221.0 /1

Function requirements for the electronic accelerator, general points
- Circuit 87M ON (engine control ON)
- Engine running

Electronic accelerator, general points
The electronic accelerator function (EFP) is integrated in the ME-SFI [ME] control unit (N3/10), and controls the engine torque according to driver requests and operating conditions.

The ME-SFI [ME] control unit regulates the engine torque according to the following sensors and signals:
- Accelerator pedal sensor (B37), accelerator pedal position
- ESP control unit (N47-5), brake actuation via the chassis CAN (CAN E)
- ESP control unit, cruise control request via the chassis CAN
- Video and radar sensor system control unit (N62/2) (for code (233) DISTRONIC PLUS for code (237) Active Blind Spot Assist for code (238) Active Lane Keeping Assist), DISTRONIC request via the chassis CAN
- Electric controller unit (VGS) (Y3/8), gear range over the engine compartment (CAN C)
- Electric controller unit (VGS), reverse travel signal via drive CAN

The requirements of the torque coordination function are also taken into account.

Function sequence for electronic accelerator
The function sequence is described in the following steps:
- Function sequence for engine torque specification
- Function sequence for drivability functions
- Function sequence for reverse travel
- Function sequence for adaptive accelerator pedal

Function sequence for engine torque specification
The ME-SFI [ME] control unit controls the engine torque according to a performance map depending on accelerator pedal sensor signals. To do this the ME-SFI [ME] control unit actuates the actuator motor (M16/6m1) in the throttle valve actuator (M16/6) by means of a pulse width modulated signal (PWM signal), the ignition angle effectiveness over the ignition timing of the ignition coils (T1) and spark plugs (R4) and the boost pressure over the boost pressure regulator (Y77/1). The engine torque is only then defined by the accelerator pedal position if there are no limiting or increasing torque requests active from other functions or control units (e.g. a CC request). The actual value potentiometers 1 and 2 (M16/6r1, M16/6r2) report the current throttle valve position to the ME-SFI [ME] control unit.

Function sequence for drivability functions
The drivability functions and throttle change damping have the task of limiting the change in the engine torque as a result of a rapid movement of the accelerator pedal. The limitation serves to improve the ride comfort since any jolting in the drivetrain is prevented.
The drivability functions and the throttle change damping take place on the basis of the following sensors and signals:
- Accelerator pedal sensor, accelerator pedal actuation (fast, slow)
- Crankshaft Hall sensor (B70), engine speed
- Coolant temperature sensor (B11/4)
- Pressure sensor downstream of throttle valve actuator (B28/7), intake manifold air pressure
- ESP control unit, vehicle speed via the chassis CAN

Function sequence for reverse travel
If the electric controller unit (VGS) transmits the CAN signal "reverse travel" via the drive train CAN, the engine torque is limited to about 50% by the ME-SFI [ME] control unit. This optimizes ride comfort and driving safety when reversing.

Function sequence for adaptive accelerator pedal
The ME-SFI [ME] control unit alters the response time of the accelerator pedal depending on the vehicle speed. A somewhat steeper accelerator pedal curve is used at high vehicle speeds in order to improve the response time (reduction of the free travel).

Further functions which support the electronic accelerator and which are described in other documents are:
- Engine speed control
- Torque coordination
- Engine limp-home mode