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Electronic accelerator pedal emergency running mode, function - GF30.20-P-4026MIG

ENGINES 272.945 in MODEL 251.054/154 as of model year 2009/AEJ 08 

ENGINES 272.967 in MODEL 164.186 as of model year 2009/AEJ 08 model refinement package 

ENGINES 272.967 in MODEL 251.056/065/156/165 as of model year 2009/AEJ 08 

ENGINES 273.923 in MODEL 164.871 as of model year 2009/AEJ 08 

ENGINES 273.963 in MODEL 164.172 as of model year 2009/AEJ 08 model refinement package 

ENGINES 273.963 in MODEL 164.886, 251.072/172 as of model year 2009/AEJ 08 

Electronic accelerator limp-home mode function requirements, general 

Limp-home mode electronic accelerator, general points 

The task of the electronic accelerator (EFP) limp-home mode consists in ensuring that the vehicle can continue to be driven safely even if there are faults in the electronic accelerator system (EA).

Limp-home is recognizable from a significantly surging engine running characteristic.

The ME-SFI [ME] control unit (N3/10) controls limp-home mode according to the following sensors and signals:

Limp-home mode electronic accelerator function sequence 

The function sequence is described in the following steps:

Limp-home mode function sequence on failure of the accelerator pedal sensor 

If a Hall sensor fails, the system switches over to the second Hall sensor. The throttle valve opening is limited to about 60% of the maximum opening. In addition, the speed at the which the throttle valve opens is dynamically limited (throttle valve opens with a delay).

If the plausibility check is negative or if both Hall sensors fail, only idle speed is then still controlled.

Limp-home mode function sequence on failure of throttle valve actual value potentiometer 1 or 2 

If one potentiometer fails, the system switches over to the second, intact potentiometer. Air mass is used as an additional comparison value.

If both potentiometers are faulty, the spring capsule brings the throttle valve to the limp-home position of about 10° opening angle.

Limp-home mode function sequence on failure of the throttle valve actuator motor 

The throttle valve actuator is de-energized and the spring capsule brings the throttle valve to the limp-home position of about 10° opening angle.

Limp-home position function sequence 

When the throttle valve IS in limp-home position, fuel is shut off/resupplied to the cylinders to limit engine speed to about 1200 to 1400 RPM at idle, and about 1800 in driving mode. If the brake pedal is operated, this always means idle speed input.

The ME-SFI [ME] control unit activates/deactivates the cylinders by switching the injection valves (Y62) on/off, according to:

IMPORTANT Diagnosis

Faults detected by the accelerator pedal sensor and throttle valve actuator are stored in the fault memory, and can be read out and deleted with the Diagnosis Assistance System (DAS).

REFER TO SYSTEM WIRING DIAGRAMS Function diagram for electronic accelerator limp-home mode Model 164   PE30.30-P-2051-97MAA 
Model 251   PE30.20-P-2051-97RAA
  ME-SFI [ME] control unit, component description N3/10 Engine 272 GF07.61-P-6000MIG
N3/10 Engine 273 GF07.61-P-6000MLG
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