gf0710p1047a

Engine limp-home mode, basic function

Typ gf · téma 07.10 · verze 0106 · 2020-09-10

Platí pro: Engine all (CAR)

Není k dispozici v jazyce „cs“; zobrazeno v jazyce Angličtina.

Zařazení

Funkční skupina 1 Motor › 07 Příprava směsi › 07.10 Elektronické řízení motoru/Regulace motoru — Řada 900 (modely 9**) · Řada 902 (modely 9**) · Řada 904 (modely 918, 919, 924, 925, 938, 943, 957) · Řada 906 (modely 917, 918, 924, 953)

Platí také pro motory/převodovky: 139 ***, 254 ***, 256 ***, 272 ***, 276 ***, 282 ***, 457 9**, 541 9**, 542 9**, 608 ***, 700 4**, 700 420, 700 421, 700 422, 700 423, 715 3**, 715 5**, 722 6**, 722 9**, 724 ***, 724 0**, 724 033, 724 044, 724 045, 724 1**, 724 103, 724 114, 724 115, 724 120, 725 ***, 725 0**, 725 035, 725 037, 725 038, 725 085, 725 1**, 739 390, 739 391, 739 395, 739 396, 739 397, 739 398, 739 399, 740 698, 743 3**, 743 4**, 743 498, 746 971, 924 9**, 924 910, 925 9**, 926 9**

GF07.10-P-1047A

Engine limp-home mode, basic function

09.09.2020

Engine

all (CAR)

Overview

This document contains information on:

General

Function requirements

Function

General

The engine limp-home mode protects the engine from damage during operation and allows continued operation with restrictions in the event that individual components of the engine management fail.

Function requirements

Engine management ON (circuit 87M)

Engine in operation

Combustion engine control unit detects a malfunction

Function

Engine limp-home mode

To ensure fault-free operation of the engine, the combustion engine control unit constantly monitors the components of the engine management. If a malfunction is detected, the combustion engine control unit activates the engine limp-home mode.

When the engine limp-home mode is active, the engine output is reduced and the engine speed limited.

General causes for engine limp-home mode

Failure of the accelerator pedal sensor

Failure of the crankshaft Hall sensor

Diesel engine: overloading of the diesel particulate filter

Malfunction in the exhaust gas turbocharger

Spark-ignition engine: failure of the throttle valve sensor

Spark-ignition engine: failure of the throttle valve actuator motor

Spark-ignition engine: limp-home position of the throttle valve

Failure of the accelerator pedal sensor

If one accelerator pedal sensor fails, the switch is made to the second accelerator pedal sensor and the engine output is limited. If both accelerator pedal sensors fail, or the plausibility test of the accelerator pedal signals fails, only the idle speed is regulated.

Diesel engine: The combustion engine control unit reduces the fuel pressure in the fuel distributor and, by actuating the fuel injectors, the injection duration for the fuel.

Spark-ignition engine: The combustion engine control unit limits the throttle valve opening to approx. 60 % of the maximum opening. In addition, the throttle valves only open with a delay.

Failure of the crankshaft Hall sensor

If the signal from the crankshaft Hall sensor fails, the signals from the intake camshaft or exhaust camshaft Hall sensors are used as a replacement for engine limp-home mode.

Diesel engine: overloading of the diesel particulate filter

If the DPF differential pressure sensor determines that the load condition is too high, the engine output is reduced.. The combustion engine control unit reduces the fuel pressure in the fuel distributor and, by actuating the fuel injectors, the injection duration for the fuel.

Malfunction in the exhaust gas turbocharger

If the exhaust gas turbocharger generates too much boost pressure, the engine output is reduced. The combustion engine control unit reduces the fuel pressure in the fuel distributor and, via the duration of the fuel injector actuation, the injection quantity of the fuel.

Failure of the throttle valve sensor

If one throttle valve sensor fails, the switch is made to the second throttle valve sensor. If both throttle valve sensors are faulty, the return spring sets the throttle valve to the limp-home position at an opening angle of approx. 5 °.

Failure of the throttle valve actuator motor

If the throttle valve actuator motor fails, it is deenergized and set to the limp-home position at an opening angle of approx. 5° by the return spring.

Limp-home mode position of throttle valve

When the throttle valve is in limp-home position, the engine speed is regulated to about 1200 to 1400 rpm at idle and about 1800 rpm in driving mode. To do this, the fuel supply to individual cylinders is shut off/activated by the combustion engine control unit. When the driver operates the brake pedal, the engine speed is regulated to the idle speed.

Function schematics

Function schematic for engine limp-home mode

Engine 608 in model 118, 177, 247

PE07.10-P-2510-97A

Engine 282 in model 118, 177, 247

PE07.10-P-2510-97B

Engine 260 in model 118, 177, 247Engine 264 in model 167

PE07.10-P-2510-97C

Engine 654 in model 118, 167, 177, 247Engine 654 in model 213, 238, 257 as of model year 2021Engine 656 in model 167, 223

PE07.10-P-2510-97D

Engine 254, 264 in model 213, 238, 257 as of model year 2021Engine 256 in model 167Engine 256 in model 213, 238 as of model year 2021

PE07.10-P-2510-97E

Engine 176, 177 in model 167

PE07.10-P-2510-97F

Engine 139 in model 118, 177

PE07.10-P-2510-97G

Engine 256 in model 223

PE07.10-P-2510-97H

Engine 176, 177 in model 223

PE07.10-P-2510-97I

Engine 279 in model 223

PE07.10-P-2510-97J

Control units

Combustion engine control unit, basic function

Engine all (CAR)

GF07.08-P-9890A

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