GF07.10-P-1019OGG Engine Limp-Home Mode, Function

GF07.10-P-1019OGG Engine Limp-Home Mode, Function
- as of model year 09

Function requirements for engine limp-home mode - general points
^ Circuit. 87 ON (engine control ON)
^ Engine running

Engine limp-home mode, general points
The task of engine limp-home mode consists of ensuring secure further driving in the case of faults on individual components of the engine control.
The CDI control unit (N3/9) controls engine limp-home mode according to the following sensors and signals:
- Camshaft Hall sensor (B6/1)
- Accelerator pedal sensor (B37), accelerator pedal position
- Crankshaft Hall sensor (B70), engine speed
- ESP control unit (N47-5), brake actuation via engine compartment CAN (CAN-C)
- Electric controller unit (VGS) (Y3/8), gear range via engine compartment CAN

Function sequence for engine limp-home mode
The function sequence is described in the following steps:
^ Limp-home mode on failure of the accelerator pedal sensor
^ Function sequence for limp-home mode in the case of failure of the crankshaft Hall sensor

Limp-home mode function sequence on failure of the accelerator pedal sensor
In the case of failure of a Hall sensor,switchover takes place to the second Hall sensor and the engine power is reduced.
To do this the CDI control unit regulates the fuel pressure in the rails via the pressure regulating valve (Y74) and the injection time over actuation of the fuel injectors (Y76).

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

Function sequence for limp-home mode in the case of failure of the crankshaft Hall sensor
If no voltage signal is received from the crankshaft Hall sensor, the voltage signal from the camshaft Hall sensor is used as a substitute (for emergency mode).

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