(Engine Limp-Home Mode, Function - GF07.10-P-1019OGR)

ENGINE 642.8 in MODEL 166

up to model year 2016

Function requirements for engine limp-home mode, general points

Circuit 87 (Engine management ON)
Engine runs

Engine limp-home mode, general

Engine limp-home mode is responsible for continued safe driving in the event of malfunctions of individual components.

The CDI control unit (N3/9) controls engine limp-home mode based on the following sensors and signals:

Camshaft Hall sensor (B6/1)
Accelerator pedal sensor (B37), accelerator pedal position
Crankshaft Hall sensor (B70), engine rpm
Electronic Stability Program control unit (N30/4), brake actuation via chassis CAN 1 (CAN E1)
Fully integrated transmission control controller unit (Y3/8), gear range over drive train CAN (CAN C)

Function sequence for engine limp-home mode

The function sequence is described in the following steps:

Function sequence for limp-home mode for failure of the accelerator pedal sensor
Function sequence for limp-home mode on failure of the crankshaft Hall sensor

Function sequence for limp-home mode for failure of the accelerator pedal sensor

In case of failure of a Hall sensor the system switches to a 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 quantity control valve (Y94) and the injection duration through the actuation of the fuel injectors (Y76).

If the plausibility check made by the CDI control unit is negative or if both Hall sensors fail, the system will only work to regulate the idle speed.

Function sequence for limp-home mode on 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 will be used instead (for limp-home mode).

Diagnosis

Faults detected by the accelerator pedal sensor are stored in the fault memory and can be read out and cleared using Xentry Diagnostics.

	Electrical function schematic for engine limp-home mode		PE07.10-P-2719-97NAC
	Overview of system components for common rail diesel injection (CDI)		GF07.16-P-9997OGR