gf0710p1019ogs

Engine limp-home mode, function

Tip gf · temă 07.10 · versiune 0102 · 2015-01-29

Valabil pentru: ENGINE 642.8 in MODEL 222

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Încadrare

Grupă funcțională 1 Motor › 07 Pregătirea amestecului › 07.10 Distribuţie electronică a motorului/reglare motor — Seria 222

Valabil și pentru motoare/cutii de viteze: 642 8**

GF07.10-P-1019OGS

Engine limp-home mode, function

14.1.15

ENGINE

642.8 in MODEL 222

Function requirements for engine limp-home mode, general points

Circuit 87 (Engine management ON)

Engine runs

Engine limp-home mode, general

The task of the engine limp-home mode consists of ensuring continued safe driving in the case of malfunctions on individual components of the engine management.

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 suspension FlexRay (Flex E), powertrain control unit (N127) and drive train CAN (CAN C1)

Fully integrated transmission control unit (Y3/8n4) (with code 427 (7G-TRONIC) or (with code 421 (9G-TRONIC), gear range via the drive train (CANC1)

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 period 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-2719-97SEB

Overview of system components for common rail diesel injection (CDI)

GF07.16-P-9997OGS

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