Electronic Accelerator Pedal Emergency Running Mode Function

Electronic Accelerator Pedal Emergency Running Mode Function

Task
To allow safe further driving depending on the fault which has arisen in the electronic accelerator pedal system.

Pedal value sensor emergency mode
If the sensor in the pedal value sensor (B37) fails, the system will switch over to the second sensor. The throttle valve opening is limited to approx. 60%. There is also dynamic limitation of the throttle valve's opening speed where the throttle valve opening is delayed (the indicator lamp EPC does not light up).
If the plausibilty check delivers a negative result or both sensors are defect only the idling speed will be regulated (the indicator lamp EPC lights up).

Actuator for the throttle valve - emergency running, electrical
If a potentiometer in the actuator for the throttle valve breaks down the system switches-over to the second intact potentiometer. The air flow mass serves as a second parameter for comparitive purposes. Following a plausibility check, the throttle valve opening is limited to approx. 60% in line with engine speed and load (EPC indicator lamp does not come on).
If the plausibility check is negative or if both potentiometers are faulty, the throttle valve adopts a mechanical emergency running position which is fixed by the spring capsule in the actuator (EPC indicator lamp comes on).

Actuator for the throttle valve - emergency running, mechanical emergency running stop
If the actuator motor is defect or there are other faults present the power supply to the actuator will be shut off. The throttle valve then lies on the mechanical stop (spring box) so the throttle valven opening remains at a constant 10-12°. At no engine load (idling) engine speed is regulated to about 900 rpm by shutting off or activating the cylinders at the fuel side.
When driving, engine speed is controlled, in line with the engine load, by switching the cylinders off and on at the fuel side. The maximum engine speed is about 1800 rpm. which is limited by the mechanical stop (the indicator lamp EPC lights up).

Safety fuel shutoff
If a mechanical fault exists in the actuator, the safety fuel shutoff is activated.
Here the fuel injection valves are shut off for engine speeds >1400 rpm and actuated again at speeds <1200 rpm (the indicator lamp EPC lights up).
Note: If the faults described above exist, read out the fault memory. The indicator lamp EPC is only installed on types 129, 140 from about 4/95 to 6/96.