Mercedes-Benz M 447 hLAG User manual

MERCEDES-Benz Service
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Mercedes-Benz AG •Omnibus Product Division •
Status September 2003 (EvoBus-Service / AFT)
Natural Gas Engine: M 447 hLAG
In Mercedes-Benz City Bus
Click bus for index
The EGM engine control unit

Foreword
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Status September 2003 (EvoBus-Service / AFT) Page: 2 of 83
This training document is intended for the technical personnel charged with the maintenance and
servicing of Mercedes-Benz omnibuses with a natural-gas power plant (M 447 hLAG).
In the contents we provide information on the working and operating modes of the engine control unit
(MR) EGM (electronic gas engine) of the M 447 hLAG.
Details are based on the software version 14B_001
(ZCRB0A01).
The specified part number serve only mark marking and distinguishing individual components. When
ordering spare parts, the part numbers should always be taken from the spare parts documentation.
This training document resulted as part of the temporary special measure "Support Start-Up Safeguarding
for M 447 hLAG" and was supplemented with the new diagnostic functions of the software 14B_001. It is
not subject to the updating service. All information correspond to the status at the time of printing.
Other applicable documents (Service – EvoBus)
Title
Operating Manual (Omnibus Model O 530 – Citaro ÜSTRA)
On-Board-Diagnose (Omnibus Model O 530 – Citaro ÜSTRA)
Maintenance Sheets, Maintenance Manual (Omnibus Model O 530 – Citaro ÜSTRA)
DC Intranet (description of the natural gas Citaro and the CNG components)
September, 2003

Abbreviations
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Status September 2003 (EvoBus-Service / AFT) Page: 3 of 83
°DK Grad DrosselKlappe (Degrees of Throttle Valve)
ABS AntiBlockierSystem – Traction Control (Antilock Braking System)
AGN Automatisches Getriebe Nutzfahrzeug
(Automatic Transmission for Commercial Vehicle)
ATL AbgasTurboLader (Exhaust-Gas Turbocharger)
ATLR AbgasTurboLaderRegler (Exhaust-Gas Turbocharger Controller)
BS Brems-Steuerung (Braking Control)
CAN Controller Area Network
CNG Compressed Natural Gas (primarily methane)
DK DrosselKlappe (Throttle Valve)
DKS DrosselKlappenSteller (Throttle Valve Actuator)
DRB DRehzahlBegrenzung (Speed Limitation)
EDW Elektronische DiebstahlWarnanlage (Electronic Alarm System)
EGM Elektronik GasMotor (Motorregelung des Erdgasmotors)
Elektronik GasMotor (Engine Control of Natural-Gas Engine)
EPW ElektroPneumatischerWandler (Electropneumatic Converter)
EV EingasVentil (Gas Injector)
FPS Flexibel Programmierte Steuerung (Flexibly Programmed Controller)
FR FahrzeugRegelung (Vehicle Control)
FSP FehlerSPeicher (Fault Memory)
H-Leitung High-Leitung (CAN - High Line)
HW HardWare
IBIS Integriertes Bord InformationsSystem
(Integrated On-Board Information System)
Kl. Klemme (Terminal)
KR KlopfRegelung (Knock Control)
KW KurbelWelle (Crankshaft)
KWS KnickWinkelSteuerung (Knee Angle Control)
KW-Sensor Drehzahlaufnehmer an der KurbelWelle (Speed Sensor on Crankshaft)
L-Leitung Low-Leitung (CAN - Low Line)
LLR LeerLaufRegler (Idling Controller)
LMR LambdaMagerRegler (Lambda Lean Controller)
LSU LambdaSondeUniversal (Universal Lambda Probe - Broadband Probe)
MR MotorRegelung (Engine Control)
NR NiveauRegelung (Level Control)
NW NockenWelle (Camshaft)
NW-Sensor Drehzahlaufnehmer an der NockenWelle
OBD OnBoardDiagnose (On-Board Diagnosis)
OT Oberer Totpunkt (Top Dead Centre)
PLD Pumpe-Leitung-Düse
(Pump Line Nozzle - Engine Control of Diesel Engine)
Prop.-Ventil (PV) ProportionalVentil (Proportional Valve)
PWM PulsWeitenModulation (Pulse Width Modulation)
SAS SchubAbSchaltung (Overrun Fuel Cut-Off)
SG SteuerGerät (Control Unit)
SW SoftWare
TV TastVerhältnis (Pulse Duty Factor)
WS WartungsSystem (Maintenance System)
ZL Zusatz-Lenkung (Additional Steering)

Table of Contents
To forward directly to relevant section, click on BOLD sections headings _____________________
Status September 2003 (EvoBus-Service / AFT) Page: 4 of 83
1 Natural Gas Engine M 447 hLAG 8
2 Functional Description of EGM 11
2.1 Introduction 11
2.2 Torque control 13
2.2.1 Engine protection functions 14
2.2.2 Idling control 27
2.3 Engine state detection 28
2.4 Cylinder filling 28
2.4.1 Throttle valve control 29
2.4.2 Throttle valve diagnosis 30
2.4.3 Turbocharger control 31
2.4.4 Turbocharger diagnosis 34
2.5 Gas injection 35
2.5.1 Gas mass calculation during starting 35
2.5.2 Gas mass calculation in normal case 35
2.5.3 Lambda control 37
2.5.4 Lambda control diagnosis 38
2.5.5 Overrun fuel cut-off (SAS) 38
2.5.6 Switch-on conditions for gas injection 38
2.6 Ignition 40
2.6.1 Firing angle in starting mode 40
2.6.2 Firing angle determination in idling mode 40
2.6.3 Firing angle determination in partial-load and full-load mode 40
3 Electrical Description of EGM 42
3.1 System interface overview 42
3.1.1 Block diagram 42
3.1.2 Connector assignment of EGM and ignition modules 43
3.1.3 Power supply of EGM 45
3.1.4 Power supply of ignition module 46
3.2 Sensor technology 47
3.2.1 Active sensors 47
3.2.2 Special sensors 47
3.2.3 Passive sensors 48
3.3 Digital inputs 49
3.3.1 Terminal 15 49
3.3.2 Terminal 50 49
3.3.3 Service switch Start/Stop 49
3.4 Actuator technology 50
3.4.1 Gas injectors 50
3.4.2 Gas injector actuation 50
3.4.3 Proportional valve actuation 52
3.4.4 Lambda heating actuation 52
3.4.5 High-pressure cut-off valve actuation 52
3.4.6 Ignition module actuation 52

Table of Contents
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4 Diagnosis 54
4.1 Reading measured values 54
4.1.1 Target engine torque (FR) 55
4.1.2 Maximum current engine torque 55
4.1.3 Actual engine torque 55
4.1.4 Gas injection angle (Cylinder 1) 55
4.1.5 Angle for start of gas delivery (Cylinder 1) 55
4.1.6 Current target control speed 56
4.1.7 Current final limit speed 56
4.1.8 Control-speed target value (FR) 56
4.1.9 Redundant speed (Ter. W) (FR) 56
4.1.10 Engine speed 56
4.1.11 Exhaust-gas temperature 57
4.1.12 Vehicle speed (FR) 57
4.1.13 Coolant temperature 58
4.1.14 Gas temperature 59
4.1.15 Calculation of gas pressure 60
4.1.16 Calculation of engine oil level 61
4.1.17 Oil temperature 61
4.1.18 Charge-air temperature 62
4.1.19 Boost pressure 63
4.1.20 Atmospheric air pressure 64
4.1.21 Oil pressure 65
4.1.22 Throttle-valve target position 66
4.1.23 Throttle-valve actual position 66
4.1.24 Lambda target value 66
4.1.25 Lambda actual value 66
4.1.26 Lambda-probe heating current 66
4.1.27 Lambda correction factor 67
4.1.28 Air mass 67
4.1.29 Gas mass 67
4.1.30 Firing angle (Cylinder 1) 67
4.1.31 Turbocharger pulse duty factor 67
4.1.32 Battery voltage 67
4.2 Reading binary values 68
4.3 EGM-specific Customer Service routines 71
4.3.1 Temporarily switch off LMR 71
4.3.2 Switch-off of gas injectors 72
4.3.3 Cylinder-selective ignition switch-off 72
4.3.4 Temporarily switch off engine run-on 73
4.3.5 Manual compression test 73
5 Checking EGM 74
5.1 Troubleshooting 74
5.1.1 Engine fails to start 74
5.1.2 Engine cannot be switched off 74
5.1.3 Increased engine idling speed 74
5.1.4 Reduced engine output 75
5.1.5 Rough engine running, traction interruption 75
5.2 Special tools 76
5.3 Circuit diagram of M 447 hLAG 76
5.4 Engine performance data 78