Electronic Throttle Actuator: Description and Operation

GF30.20-P-3015MM Electronic Accelerator Function
ENGINES 276.9 in MODEL 204.0 /2 /3 /9, 207.3 /4, 212.0 /2, 218

Function requirements for the electronic accelerator, general
^ 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 opening angle of the throttle valve according to driver requests and operating conditions.
The ME-SFI [ME] control unit regulates the throttle valve position according to the following sensors and signals:
- Accelerator pedal sensor (B37), accelerator pedal position
- Electronic Stability Program control unit (N30/4) (except code (233) DISTRONIC PLUS) or Electronic Stability Program Premium control unit (N30/7) (for code (233) DISTRONIC PLUS), brake actuation via the chassis CAN (CAN E)
- Electronic Stability Program control unit cruise control request, over the chassis CAN
- Video and radar sensor system control unit (N62/2) (with code (233) DISTRONIC PLUS, with code (237) Active Blind Spot Assist, with code (238) Active Lane Keeping Assist), engine torque request via the chassis CAN
- Fully integrated transmission controller unit (Y3/8) gear range, via the drive train CAN (CAN C)
- Fully integrated transmission controller unit, reverse travel signal via the drive train CAN

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

The Electronic Stability Program control unit (N30/4) will be introduced into service as of 1.3.2011 (model 204.0/2) or as of 1.6.2011 (model 204.3) in 2 variants:
- Electronic Stability Program control unit, Basis variant (except code (233) DISTRONIC PLUS)
- Electronic Stability Program control unit, Premium variant (except code (233) DISTRONIC PLUS)

From 1.6.2011 only the basic variant of the Electronic Stability Program control unit will be used in model 204.9.

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 dependent on a performance map dependent on the accelerator pedal sensor. To do this the ME-SFI [ME] control unit controls the actuator motor (M16/6m1) in the throttle valve actuator (M16/6) by means of a pulse width modulated signal (PWM signal), the effectiveness of the ignition angle over the ignition timing of the ignition coils (T1) and spark plugs (R4), the fuel mass/lambda value over the fuel injectors (Y76).

The engine torque is then only determined by the accelerator pedal position if no limited or increased torque requests from other functions or control units (e.g. cruise control request) are active. The actual value potentiometers 1 and 2 (M16/6r1, M16/6r2) report the current throttle valve position to the ME-SFI [ME] control unit.
The position feedback of the throttle valve actuator takes place by means of a contact-less angular sensor.

Function sequence for drivability functions
The drivability functions and throttle change damping have the task of limiting the change of engine torque as a result of a rapid movement of the accelerator pedal. The limitation serves to improve the ride comfort since jolting in the drive train is prevented.

The drivability functions and the throttle change damping takes 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) (model 204, 207, 212), coolant temperature sensor (B11/4) (model 218)
- Hot film MAF sensor (B2/5), engine load (for an engine with stratified operation)
- Left and right oxygen sensors upstream of catalytic converter (G3/3, G3/4)
- Left and right oxygen sensors downstream of catalytic converter (G3/5, G3/6)
- ESP control unit, wheel speed via the chassis CAN

Function sequence for reverse travel
If the fully integrated transmission control controller unit 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 changes the actuation characteristics of the accelerator pedal depending on the vehicle speed calculated from the wheel speed. At higher vehicle speeds a somewhat steeper accelerator pedal curve is used 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