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Home >> Mercedes Benz >> 2007 >> S550 Base >> Repair and Diagnosis >> Accessories & Equipment >> Cruise Control Systems >> Throttle Control, Speed Control Systems -- Basic Knowledge -- S-Class (221) >> Basic Knowledge >> Electronic accelerator pedal emergency running mode, function - GF30.20-P-4026M

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

ENGINE 275.950 in MODEL 215, 220 

ENGINE 275.951 in MODEL 230 up to Model Year 8 

ENGINE 275.953 in MODEL 216, 221 up to Model Year 8 

ENGINE 275.954 in MODEL 230 up to Model Year 8 

ENGINE 275.980 in MODEL 215, 220 

ENGINE 275.981 in MODEL 230 up to Model Year 8 

ENGINE 275.982 in MODEL 216, 221 up to Model Year 8 

ENGINE 285.950 in MODEL 240 

ENGINE 285.980 in MODEL 240 

Illustrated model 215, 220, 230, 240 

Fig 1: Electronic Accelerator Pedal Emergency Running Mode Function Diagram
G07622894Courtesy of MERCEDES-BENZ USA

The task of the emergency running consists of enabling a safe continuation of journey if interference occurs at the electronic accelerator.

Accelerator pedal sensor, emergency mode 

If a Hall sensor fails, the system switches over to the second Hall sensor. The throttle valve opening is limited to approx. 60%. In addition, the throttle valve opening rate is dynamically limited, in other words the throttle valve opens with a time delay. If the result of the plausibility check is negative, or if both potentiometers are faulty, only the idle speed is then controlled.

Throttle valve actuator, emergency mode (electrical) 

If a potentiometer fails, the system switches over to the second potentiometer. The signal from the pressure sensor downstream of throttle valve actuator serves as an additional comparative size.

If the plausibility check is negative or if both potentiometers are faulty, the throttle valve adopts a mechanical emergency running position (approx. 8 to 10°) which is fixed by the spring capsule in the throttle valve actuator (EPC malfunction indicator lamp comes on).

Throttle valve actuator, emergency mode (mechanical) 

If the actuator motor is defective or there are other faults present, the power supply to the throttle valve actuator will be shut off.

The throttle valve is resting against the mechanical stop (spring capsule) as a result of which the throttle valve opening is maintained constantly at approx. 8 to 10°.

In neutral at engine speeds of > 1400/min, the fuel injection valves are deactivated and at engine speeds of < 1200 RPM actuated again.

While driving, depending on the engine load, engine speed is controlled by switching the cylinders on and off on the fuel side. The maximum engine speed is approx. 1800 RPM and is fixed by the mechanical stop.

IMPORTANT Faults detected by the accelerator pedal sensor (B37) and the throttle valve actuator are stored in the fault memory and can be read out and deleted with STAR DIAGNOSIS.

Emergency mode is recognizable on a clearly surging engine running.

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Transmission 722.6
GF27.19-P-4012G