Functional Description Of Egm; Introduction - Mercedes-Benz M 447 hLAG Service Manual

_____________________________________________________________________

2 Functional Description of EGM

2.1

Introduction

The EGM (electric gas engine) engine control unit is mounted on the engine, and is therefore part of the
engine. Only one basic control unit is required for all offered output variants
EGM is adapted to the corresponding output and engine variant with different programming. An EGM that
is already programmed is considered a special engine component and may not be interchanged between
different engines. An exchange of the EGM can lead to problems ranging from impairment of correct
engine operation to engine and drive train damage. Exchange engines are always delivered complete with
the engine wiring harness and the related EGM engine control
unit.
To be able to distinguish between different control units,
each unit is provided with a sticker. The data record number
(1) with which the EGM is programmed is indicated at the top
of the sticker. This data record number should always be
specified when purchasing a replacement.
The EGM engine control unit is an electronic spark-
ignition engine control unit for engines of the 447 and 900
series. The EGM's design is based on the PLD diesel engine
control unit and is virtually identical to the PLD on the
outside. Open and closed-loop control functions which can be
used both for diesel and spark-ignition engines have been
adopted from the PLD in the EGM. Examples include:
•
Engine control with torque interface
•
Camshaft/crankshaft signal detection
•
CAN and ISO-K interfaces
•
Oil level sensing
•
PIN assignment of vehicle connector
•
Service engine switch Start/Stop
•
Starter control
The functions specific to spark-ignition engines have been newly developed. The main open and closed-
loop control functions are:
•
Air mass control by electronic throttle valve and boost-pressure control
•
Dwell and firing-angle control
•
Sequential gas injection with variable start of gas injection
•
Lambda control with broadband probe for lambda = 1 and lean operation
•
Engine protection functions
•
Diagnostic functions
1
The output variants with 185 kW (rigid vehicle) and 240 kW (articulated vehicle) are currently available
Status September 2003 (EvoBus-Service / AFT)
Functional Description of EGM
1
of the M 447 hLAG. The
Page: 11 of 83