sistema de combustible con inyector bomba pde y edc s6. descripción de funcionamiento

8/12/2019 Sistema de Combustible Con Inyector Bomba PDE y EDC S6. Descripcin de Funcionamiento

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Scania CV AB 2004, Sweden

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03:04-09Issue 1 en

Fuel system with unit injector PDE

and EDC S6

Function Description

EDC

S61352

61


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Contents

Important ..................................................................................3

General ..................................................................................4

The path of the fuel...................................................5

Fuel quantity and injection timing............................ 7

Components in the fuel system Feed pump ................................................................8

Hand pump ...............................................................9

Fuel manifold..........................................................10

Pressure relief valve................................................10

Unit injector............................................................11

Fuel filter ................................................................17

EDC Overview ................................................................18

Components on the engine .....................................19

Components in the driver area................................32

Warning system ......................................................38

Interaction with other systems................................42

Contents


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03:04-09 Scania CV AB 2004, Sweden 3

Important!

The safety precautions and warnings in the work

description must be read thoroughly before anywork is carried out.

Using only the function description as a basisfor the work is not permitted.

Important


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4 Scania CV AB 2004, Sweden 03:04-09

General

A fuel system with EDC, Electronic Diesel

Control, and unit injectors PDE, Pumpe- Dse-Einheit, consists besides the fuel lines and a

fuel tank of the following parts.

1 A feed pump

2 A hand pump

3 An electronic control unit

4 A fuel filter

5 One unit injector, of type PDE, per cylinder

6 A fuel manifold

7 a pressure relief valve

The fuel system also includes an electroniccontrol system. The control system consists of besides the control unit the unit injectorsolenoid valves, sensors and other controlunits, among other things. More informationabout the electronic control system can be

found in the section EDC.

General


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The path of the fuel

The feed pump 1 draws fuel from the fuel tankand presses it through the fuel filter 2 and intothe fuel manifold 3.

A hand pump 4 is located on the feed pump. Thehand pump is used to bleed the fuel system.

There is an overflow valve 5 on the fuelmanifold. The pressure relief valve constantlyregulates the fuel pressure. When the pressure istoo high, the pressure relief valve opens, so thatthe excess fuel is returned to the fuel tank.

The fuel rail distributes the fuel to the unitinjectors in each cylinder head. The EDC

control unit controls when the unit injectors areto inject the fuel into the cylinders.

Any excess fuel returns to the fuel tank via anunpressurised return line in the fuel manifold.

134

117

2

5

4 1

3



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Schematic diagram of the fuel system

1 2 3

D

4

E5

A

B

C

A

6 134

540

1 Feed pump

2 Hand pump3 Fuel filter

4 Cylinders

5 Fuel tank

6 Fuel duct for return and excess fuel

A Check valve

B Gear pump (feed pump)C Safety valve

D Overflow valve

E Drain union



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Fuel quantity and injectiontiming

Each unit injector consists of a pump element, asolenoid valve and a nozzle. In this way, it is

possible to control the fuel injection for eachindividual cylinder.

EDC, Electronic Diesel Control, is theelectronic system that controls both how muchfuel each unit injector should inject into thecylinder and also when the unit injector shouldinject the fuel. This control of the injectionmeans that we can optimise the combustion,which in turn leads to cleaner exhaust gases andlower fuel consumption. The EDC system

described in this booklet is designated S6.The control unit is the brain of the EDC system.The control unit processes the information bothfrom the sensors and the components that arepart of the EDC system and also from thecontrol units in other systems. When the controlunit has processed the information, it thentransmits signals to the unit injectors. Thesignals control the injection of the fuel.

The EDC system makes possible such functions

as cruise control, hand throttle, speed limiter,smoke limiter and a special cold startprogramme.

Fuel quantity and injection timing


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Components in the fuel system

Feed pumpThe gear-type feed pump is positioned on therear end of the air compressor and is driven bythe crankshaft of the compressor.

Its capacity is adjusted to deliver the rightpressure and flow rate to all unit injectors.

The hole drilled in the flange of the feed pump isused to indicate leaks.

Feed pump location

1345

90



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Hand pump

The hand pump is positioned on the rear end ofthe feed pump and is used for bleeding the fuelsystem. On buses, the hand pump is positioned

so that it is easily accessible through the rearengine compartment door.

Location of the hand pump on the feed pump ontrucks.

134

588

Location of the hand pump on buses.



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Fuel manifold

The fuel manifold distributes the fuel into theunit injectors for each cylinder head. The fuelmanifold is fastened with banjo screws that are

connected to the return line to the fuel tank.

Pressure relief valve

The pressure relief valve is positioned on thefuel manifold.

The pressure relief valve controls the supplypressure in the fuel system.

Pressure relief valve location on trucks

134

162



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Unit injector

General

There is one unit injector for each cylinder. Theunit injector is positioned in the centre of thecylinder head between the four valves.

The unit injector is a pump element forming asingle unit with the injector nozzle. It is drivenby the engine camshaft. The drive is transferredfrom the camshaft via a roller tappet, pushrodand rocker arm to the unit injector.

Any excess fuel remaining in the unit injectorafter combustion returns to the fuel tank via the

excess fuel duct (A).

A fuel duct passes through the valve housingwhich has a constant flow of fuel. The fuel thatflows through the unit injector operates likecoolant in the unit injector. The heated fuelreturns to the fuel tank via the fuel duct forreturn fuel (B).

1 Pump section

2 Injector section

3 Valve housing

A Excess fuel duct

B Fuel duct for return fuel



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The unit injector consists of three main parts.

Pump section, containing cylinder andplunger, corresponding to the pump elementin an injection pump.

Injector section, with nozzle sleeve, nozzleneedle and spring.

Valve housing, with an electromagneticallycontrolled fuel valve.

The lower part of the unit injector is fitted in asteel sleeve with copper washer resting againstthe bottom of the cylinder head, similar to anordinary injector.

The upper part of the unit injector, with

compression spring and valve housing, islocated above the cylinder head. Injectiontiming and the amount of fuel to be injected aredetermined by the control unit. The control unitcontrols the electromagnetic fuel valve in theunit injector valve housing.

The opening duration of the injector (injectortiming) determines the amount of fuel that isinjected into the cylinder.

Any excess fuel from the unit injector flows to

the fuel manifold via the duct in the cylinderhead. The fuel then runs into the return duct inthe fuel manifold via a banjo union in theoverflow valve and back to the fuel tank.



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Filling phase

During the filling phase, pump plunger 2 movesup to its highest position.

The highest point of the cam on the camshaft

has passed and the roller tappet is movingtowards the camshaft base circle.

Fuel valve 1 is in the open position and fuel canflow into the barrel from fuel duct 3.

Filling continues until the pump plunger reachesits highest position.

1 Fuel valve

2 Pump plunger

3 Fuel duct, inlet

4 Fuel duct, outlet

1

2

3

1341

41

4



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Spill phase

The spill phase begins when the camshaft hasmoved on to the position in which the cam onthe camshaft starts to press pump plunger 2down by means of the roller tappet, pushrod and

rocker arm.

The fuel can now flow through fuel valve 1,through the hole in the unit injector and outthrough fuel duct 4.

The spill phase continues as long as fuel valve 1remains open.

1 Fuel valve

2 Pump plunger

3 Fuel duct, inlet

4 Fuel duct, outlet

1341

42

1

2

3

4



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Injection phase

The injection phase begins when fuel valve 1closes. The fuel valve closes when voltage isapplied to the solenoid valve. The cam on thecamshaft continues to press pump plunger 2

down by means of the rocker arm and injectiontakes place since the passage through the fuelvalve is closed.

The injection phase continues as long as fuelvalve 1 remains closed.

1 Fuel valve

2 Pump plunger

3 Fuel duct, inlet

4 Fuel duct, outlet

134

143

1

2

3

4



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Pressure reduction phase

Injection stops when fuel valve 1 opens and thepressure in the unit injector drops below thenozzle's opening pressure.

The fuel flows through the open fuel valve 1, thehole in the unit injector and out through fuelduct 4.

It is the closed or open position of the fuel valvewhich determines when injection should beginand end.

The length of time the fuel valve remains closeddetermines the amount of fuel that is injectedduring each pump stroke.

1 Fuel valve

2 Pump plunger

3 Fuel duct, inlet

4 Fuel duct, outlet

1341

44

1

2

3

4



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Fuel filter

The fuel filter is an insert filter with one filterelement. The filter element is secured to the lidand when the filter is removed, the filter housing

drains automatically.

Fuel filter location

134

587

In and outlets of the fuel filter on trucks1 Bleeder nipple

2 Intake

3 Outlet

4 Return to fuel tank

5 Return from fuel manifold

In and outlets of the fuel filter on buses1 Bleeder nipple

2 Intake

3 Outlet

4 Bleeder nipple (used when the fuel tank istoo high for the other bleeder nipple to beused.)



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EDC S6

Overview

The figure below illustrates the components andsystems with which the EDC control unitcommunicates. Communication with certaincomponents takes place via the coordinator.

3 4

5

6

1

78

2

PDE

13

42

539

1 Two engine speed sensors

2 Charge air pressure and temperaturesensor

3 Coolant temperature sensor

4 Oil pressure sensor

5 Unit injector solenoid valves, one percylinder.

6 Coordinator that connects the EDC

control unit to the components in the driverarea.

7 Control unit for Opticruise

8 Control unit for Retarder

9 Control unit for ABS/TC and EBS

Overview


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Components on the engine

Engine speed sensors, T74 and T75

1 Engine speed sensor 1, T74

2 Engine speed sensor 2, T75

1345

91

T74T75

Engine speed sensor location. The detail showssome of the holes in the flywheel that aredetected by the engine speed sensors.

There are two engine speed sensors in the EDCsystem, engine speed sensor 1 and engine speedsensor 2. The sensors are inductive. This meansthat they only produce signals when the engineis running. The signal strength variessignificantly, depending on the air gap betweenthe sensors and the flywheel as well as on theengine speed. The EDC system performs anassessment of the signal strength at differentengine speeds. If the signal strength becomestoo low, a fault code is generated.

Both engine speed sensor 1 and engine speedsensor 2 read the position of the flywheel. Thismeans that the system cannot determine whichof two possible revolutions the engine is at, i.e.whether cylinder 1 or cylinder 6 is at the ignitionposition for example. Every time the engine isstopped and the voltage cut off, the engineposition is stored. Next time the voltage isswitched on, the stored position of the engine isused to determine which revolution the engine isat. When the engine has started, a system check

is performed to verify that the stored position iscorrect.



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The EDC control unit receives signals from bothengine speed sensors. If the control unit receivesa faulty signal or no signal at all from either ofthe engine speed sensors, the engine torque islimited for safety reasons. If the control unitreceives a correct signal, the engine will behavenormally again.

If the control unit receives a faulty signal or nosignal at all from both engine speed sensors, theengine cannot be started. If the engine isrunning, it will be turned off.

The engine speed sensors detect the holes in theflywheel when the flywheel rotates and sendpulses to the control unit for each hole. Thisallows the control unit to calculate where in theoperating cycle the engine is. The control unitsenses and compares the engine speed atcombustion in each cylinder. The control unitseeks to keep the acceleration from eachcylinder constant by adjusting the fuel volumeindividually for each cylinder.

The interval between two of the holes is greaterthan the intervals between the remaining holes.When the control unit senses that this largerinterval passes the sensor, it knows that theflywheel is in a specific position in relation to

top dead centre (TDC UP).

If the control unit detects any faults, one or morefault codes are generated.

Engine speed sensor connections to EDCcontrol unit E44.

21

T 74 T 75

21

1 2 1 2

118

080E44

n n

A5 A6



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Charge air pressure and temperature sensors, T47

Sensor location

1345

67

T47The sensors for charge air pressure andtemperature are integrated into one single

component. Both sensors are described in moredetail on the next page.

Sensor connection to EDC control unit E44.

1 23 4

118

081

T 47

1 2 3 4

E44

P/

A10



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Charge air pressure sensor

The charge air pressure sensor detects theabsolute pressure in the intake manifold, i.e. theatmospheric pressure plus the positive pressureprovided by the turbocharger.

The EDC control unit uses the signal from thesensor to limit the fuel volume when the chargeair pressure is under a certain level. The lowerthe pressure, the less fuel the control unit allowsto go out to the unit injectors. In this way blacksmoke is avoided.

The control unit reads the voltage from thesensor. The signal voltage is directlyproportional to the charge air pressure. A highpressure gives a high voltage and vice versa.

Depending on factors such as throttle actuation,engine speed, engine acceleration and charge airtemperature, the control unit will expect acertain value for the charge air pressure. Thedeviation between the current charge airpressure and the pressure expected by thecontrol unit can be read off using ScaniaDiagnos.

If there are any faults in the signal, a fault codeis generated. The control unit will then operate

according to a pre-programmed pressure value.As a safety precaution, the engine torque is thenlimited.

Charge air temperature sensor

The charge air temperature sensor detects thetemperature in the intake manifold. The EDCcontrol unit uses the signal from the sensor tofinely adjust the fuel quantity so that blacksmoke is not produced. The warmer the charge

air, the less fuel the control unit allows to go outto the unit injectors.

The sensor is of the NTC type, which means thatits resistance is temperature dependent. If thetemperature increases, the resistance in thesensor drops.

If the voltage is outside a certain range, thecontrol unit will operate according to a pre-programmed temperature value, and a fault codewill be generated at the same time.

The engine will then react more slowly thannormal when actuating the throttle in coldweather, as the EDC control unit thinks that theair is warmer than it really is.



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Coolant temperature sensor, T33

Coolant temperature sensor location

13

4

166

T33

The coolant temperature sensor affects the fuelvolume and injection timing when starting theengine and when the engine is cold. It also

affects the engine idling speed and maximumengine speed when the engine is cold and theengine power when it is too warm.

If the coolant temperature sensor senses that theengine is cold when attempting to start (coldstart), the following will occur. If the enginedoes not start within 2 seconds, the fuel quantityinjected will successively increase until theengine starts.

Directly after a cold start, the engine speed islimited to 1000 rpm in order to protect theengine, the engine idling speed is raised to600 rpm.

The length of time engine speed limitation isengaged varies depending on the coolanttemperature:

The engine idling speed returns to normal whenthe coolant has reached 20 - 60C (thetemperature limit differs between engine types).

Below +10C 30 seconds

Above +20C 3 seconds

Coolant temperature sensor connections to EDCcontrol unit E44.

1 2

T 33

1 2

118

082E44 A7



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In certain engines, the engine power is limitedwhen the coolant temperature exceeds 104C.Refer to diagram. The engine power is limitedso that the engine does not overheat, and a faultcode is generated at the same time.

The control unit reads the voltage from thesensor. If the voltage is outside a certain range,the control unit will operate according to a pre-programmed temperature value.

The engine will then have poorer cold-startcharacteristics and will emit more white smokein cold weather.

104 106

100

o/o

o

C

118

488



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Oil pressure sensor, T5

The oil pressure sensor registers the pressure ofthe engine oil.

The EDC control unit reads the voltage from the

sensor. If the signal voltage is outside a certainrange, the oil pressure sensor on the instrumentpanel will show 0 bar, regardless of enginespeed, and a fault code will be generated at thesame time.

The EDC control unit expects a certain oilpressure depending on the engine speed. Below1000 rpm, the oil pressure should be at a certainlevel. Over 1000 rpm the oil pressure should beat a higher level, in order to provide sufficientoil pressure for piston cooling, etc. If the oilpressure is below the permitted value, the oilpressure lamp comes on. The oil pressure lamptherefore lights at different pressure levelsdepending on the engine speed.

Oil pressure sensor location

1341

67

T5

Oil pressure sensor connection to EDC controlunit E44.

32 4

1 2 3 4

118

0 8 3

T 5

E44

P/

A9



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EDC control unit, E44

Engine control unit location

134

585

E44

The EDC control unit collects informationwhich is processed into signals that control thefuel volume and injection timing solenoid

valves.

We know that the electrical system of thevehicle has a system voltage of +24 V and isearthed via the chassis.

The control unit converts the system voltage to alower voltage of approximately 5 V, which itsupplies to sensors, etc. These sensors arealways earthed through the control unit.

The control unit can be configured using Scania

Programmer. For example, a maximum speedcan be set up.

Every time the control unit is configured, thedate and VCI identification number are stored inthe memory of the control unit. This is theequivalent of security sealing.



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Sensor group

Coolant temperature sensor, T33, charge airpressure sensor, T47 and charge air temperaturesensor T47 form one sensor group. This meansthat the voltage supply from the control unit is

common to both sensors. If, for example, onesensor is short-circuited it may also affect theother.

The sensor group includes:

Coolant temperature sensor, T33

Charge air pressure sensor, T47

Charge air temperature sensor, T47

Power supply to sensors

1341

18

T33

E44

A7 A10

1

T47

1 4

1 1 4

P



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How the pins are connected is shown below.

Connectors Pin

A1 1 Power supply, +24 V to the solenoid valve for cylinder 2,

(V16).

A1 2 Power supply, +24 V to the solenoid valve for cylinder 5,(V28).

A1 3 Not used.

A1 4 Not used.

A1 5 Not used.

A1 6 Earthing of the solenoid valve for cylinder 2, (V16).

A1 7 Earthing of the solenoid valve for cylinder 5, (V28).

A1 8 Not used.

A1 9 Not used.

A1 10 Not used.

A2 1-10 Not used.

A3 1-2 Not used.

A4 1-2 Not used.

A5 1 Input signal from engine speed sensor 1, (T74).




A7 1 Input signal from the coolant temperature sensor, (T33).

A7 2 Earth for coolant temperature sensor, (T33).

A8 1-2 Not used.

A9 1 Not used.

A9 2 Voltage supply, +5 V to the oil pressure sensor, (T5).

A9 3 Input signal from the oil pressure sensor, (T5). The controlunit detects the voltage level between pins 3 and 4.

A9 4 Earth for oil pressure sensor, (T5).

A9 5 Not used.

A10 1 Supply voltage, +5V to the charge air pressure and

temperature sensor, (T47).



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A10 2 Input signal from the charge air pressure sensor, (T47). Thecontrol unit detects the voltage level between pins 2 and 3.

A10 3 Earthing of charge air pressure and temperature sensor,

(T47).

A10 4 Input signal from the charge air temperature sensor, (T47).The control unit detects the voltage level between pins 3 and4.

A10 5 Not used.

B1 1 Voltage supply, +24 V to the control unit.

B1 2 Earth connection for the control unit to chassis.

B1 3 Input signal +24 V from the starter lock (when the key is in

the drive position).

B1 4 Not used.

B1 5 Not used.

B1 6 Voltage supply, +24 V to the control unit.

B1 7 Earth connection for the control unit to chassis.

B1 8 Not used.

B1 9 CAN communication, H lead

B1 10 CAN communication, L lead

B2 1 Power supply, +24 V to the solenoid valve for cylinder 1,(V14).


B2 3 Not used.


B2 5 Not used.

B2 6 Earthing of the solenoid valve for cylinder 1, (V14).

B2 7 Earthing of the solenoid valve for cylinder 4, (V26).

B2 8 Not used.

B2 9 Earthing of the solenoid valve for cylinder 3,(V15).

B2 10 Not used.

B3 1-2 Not used.

B4 1-2 Not used.

Connectors Pin



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B5 1-2 Not used.

B6 1-2 Not used.

B7 1-2 Not used.

B8 1-2 Not used.

B9 1-5 Not used.

B10 1-5 Not used.

Connectors Pin



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Components in the driver area

The components in the driver area belong to the

coordinator. The EDC control unit will then onlyreceive a CAN message about the status of thecomponent. The components are described inthe function description for the coordinator.Below is a short description of how the EDCcontrol unit uses the information from thecoordinator.

Accelerator pedal sensor

The EDC control unit receives a CAN message

from the coordinator about the position of theaccelerator pedal. The EDC control unit uses theinformation to control the fuel volume andinjection timing solenoid valves.

Control for cruise control S51

The EDC control unit receives a CAN messagefrom the coordinator about the cruise controlsettings. The EDC control unit interprets theinformation as a desired vehicle speed or adesired engine speed and then regulates the

vehicle speed or engine speed.

Brake pedal switches

The EDC control unit receives a CAN messagefrom the coordinator about the status of thebrake pedal switches. The control unit uses theinformation to control certain functions, e.g.

Cruise control.

Clutch pedal switch

The EDC control unit receives a CAN messagefrom the coordinator about the status of theclutch pedal switches. The control unit uses theinformation to control certain functions, e.g.

Cruise control.



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Tachograph O4

The EDC control unit receives a CAN messagefrom the coordinator about the vehicle speed.Vehicle speed sensing is a pre-condition for

certain functions, e.g. Cruise control and Speedlimitation.

If the EDC control unit does not have any

information on the vehicle speed, it operates

according to the pre-programmed speed of

15 km/h.

Warning lamp for EDC, W27

The EDC control unit sends information to thecoordinator about whether the indicator lampshould be lit or not.

The indicator lamp lights for a few secondswhen the ignition is switched on to ensure that itworks.

When the engine is switched off, the indicatorlamp comes on while the EDC control unitcarries out a functional check of the EDC

system. When the check is complete, the lampgoes out.

When the engine is running, the warning lampshould normally be off. If there is a fault in theEDC system, the warning lamp comes on.

If the indicator lamp flashes continuously andthe vehicle cannot be started, a serious fault hasoccurred in the control unit. It will then beimpossible to establish contact with the control

unit. The control unit must be renewed.



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Cruise control

Cruise control

Note: Set the switch to the OFF position whenthe cruise control is not in use. In the ONposition the cruise control may be engaged bymistake.

Below is a description of the cruise controlfunctions.

Connection

The road speed must be at least 20 - 35 km/h(the speed limit varies between engine types) for

cruise control to be used.

1 Set the switch to ON.

2 Drive at the desired road speed. Press ACCor RET to engage the cruise control andthen release the accelerator pedal.

Setting the road speed

Alter the set road speed using ACC or RET.Release ACC/RET when the desired road speedis attained.

Pressing and releasing once alters the road speedby 1 km/h.

ON EngagedOFF Disengaged

ACC Accelerate

RET Decelerate (reduce vehicle speed)

RES Resume selected speed03_

0767



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Deactivation

The cruise control is disengaged by activatingone of the following:

Retarder or exhaust brake

The cruise control switch. Press it gentlytowards OFF (the spring-loaded position).

Brake pedal

Clutch pedal

Accelerator pedal - greater vehicle speedthan the set value for at least 30 seconds

Resuming the set speed

After braking for example, it is easy to quicklyselect the previous road speed by pressing RES.

The previously set value is stored until theengine is switched off or a new value is selected.



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Hand throttle

The hand throttle is used to set the desiredengine speed, e.g when operating a crane. It isset via the cruise control. The hand throttle can

be used in stationary vehicles and when drivingat low speed, maximum 10 km/h.

If the vehicle is to be driven, a gear must beengaged and the clutch pedal released before thehand throttle can be used.

Connection

1 Put the cruise control switch in the ONposition.

2 Press RES, the engine will maintain thepreviously selected engine speed.

3 Press ACC or RET to select a new enginespeed.

4 Then press RES for at least three seconds tostore the engine speed.

The engine speed remains stored until a newvalue is set, even when the engine is switched

off.

Switching over to idling speed

Press OFF

or

depress the brake or clutch pedal

or

activate the exhaust brake or the retarder.

03_

0767



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Idling speed adjustment

The engine idling speed can be adjustedbetween 500 and 700 rpm. It is adjusted via thecruise control. Generally speaking, the idlingspeed should be the lowest speed at which the

engine runs smoothly.

When adjusting it, the brake pedal must bedepressed and the engine should be warmed up(coolant temperature more than +40C).

1 Run the engine until it reaches normaloperating temperature.

2 Put the cruise control switch in the ONposition.

3 Depress the brake pedal and keep itdepressed until the engine speed is set.

4 Press RES for at least three seconds. Thiswill set the basic setting 500 rpm

5 Adjust the desired idling speed by pressingACC or RET. Every press corresponds to10 rpm.

6 Press RES for at least three seconds. Theengine speed is now set.

7 The brake pedal can now be released.

The idling speed remains stored until a newvalue is set, even when the engine is switchedoff.



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Shutdown test

Every time the engine is switched off, the EDCcontrol unit carries out a special test of the EDCsystem. While this shutdown test is running, thewarning lamp is lit. When the check is complete,

the following occurs: The control unit switchesoff and the lamp goes out. The control unitreceives battery voltage all the time.

If the control unit discovers a fault during theshutdown test, the warning lamp will come onthe next time the engine is started, even if thefault is no longer present. The control unit mustcarry out a fault-free shutdown test before thewarning lamp goes out.

Warning system


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Fault codes

When the control unit discovers a fault, orsomething which it interprets as abnormal, itgenerates a fault code. The warning system cangenerate approx. 125 different fault codes. One

flashing code in EDC S6 corresponds to severaldifferent fault codes.

Arrangement of flashing codes

The flashing codes which are flashed out by thediagnostics lamp are arranged in a certain way.The long flashes -1 second - shown firstrepresent tens. The shorter flashes - 0.3 seconds- that follow represent units.

The example to the right symbolises flashingcode 25.

106

157

A single very long flash of 4 seconds indicatesthat no fault codes are stored in the memory. 106

158

Warning system


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Fault code memory

The EDC control unit memory has sufficientcapacity to store a maximum of 40 fault codes.

The fault codes are stored in two different places

in the control unit. Erasing with the diagnosticswitch erases the fault codes that are flashed onthe diagnostic lamp.

However, the fault codes will remain stored inanother memory that can only be accessed usingScania Diagnos. Scania Diagnos can be used tosee how many times each fault has occurred;this information can be valuable with a looseconnection for example. Scania Diagnos is usedto erase both fault code memories at the sametime.

Limp-home mode

If the accelerator pedal sensor potentiometerfails, a fault code will be generated in thecoordinator. A fault code will also be generatedin the EDC control unit to report that there is a

fault in the coordinator. The vehicle can,however, be driven to the nearest workshop inlimp-home mode. Limp-home mode is activatedby releasing the accelerator pedal once so thatthe EDC control unit is aware that the throttleactuation switch works.

When the accelerator pedal is then depressed thethrottle actuation switch is closed. The closedthrottle actuation switch gives a throttleactuation equal to half of full throttle.

When the accelerator pedal is released, theengine will run at idling speed.

If the idling switch is faulty the engine will runat 750 rpm.

Warning system


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Interaction with other systems

ABS/TC and EBS

The ABS/TC system influences the EDC systemand vice versa.

The ABS/TC control unit continuously senses ifone of the driving wheels is spinning. TC enginecontrol is activated when the driving wheelsspin and the throttle actuation is then reduced,irrespective of the accelerator pedal position,until they cease to spin.

The EDC control unit receives a CAN messagefrom the coordinator about the position of theaccelerator pedal. The EDC control unitforwards information about the acceleratorpedal position to the ABS/TC control unit.

The EBS and ABS/TC control unitscommunicate with the EDC control unit in thesame way.

Opticruise

Opticruise influences the EDC system and viceversa.

The Opticruise control unit continuouslyreceives information from the EDC control unitabout data such as engine speed or acceleratorpedal position. The EDC control unit receives aCAN message from the coordinator about theposition of the accelerator pedal.

During gear changing, the Opticruise control

unit takes control of the EDC system andcontrols throttle actuation.



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Exhaust brake

The exhaust brake influences the EDC system,but not vice versa.

When the exhaust brake is activated, a message

is sent to the EDC control unit, which thendeactivates the cruise control.

When the exhaust brake is activated via thebrake pedal, the fuel supply is switched off.

Retarder

The retarder influences the EDC system andvice versa.

When the retarder is activated, a message is sent

to the EDC control unit, which then deactivatesthe cruise control.

If the accelerator pedal is depressed while theretarder is activated, the retarder willimmediately be deactivated and the vehicle willrespond to the accelerator pedal.



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PWM signals

Note:A PWM signal cannot be reliablymeasured using an ordinary multimeter. Instead,use the fault codes to locate the cause of anypossible malfunctions.

PWM means that a signal is Pulse WidthModulated.

The PWM signal is a square wave with aconstant frequency (T). The voltage level (U) isalso constant; the variable is the activation timecalculated as a percentage of each cycle (thecycle is shown as 100% in the illustrations).

The PWM signal transmits very accurate

information.

U

T

10%

100%106

159

U

T

100%

90%

1061

60



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CAN communication

Note: Bodywork builders and coachbuildersmust not connect their own systems to the CANnetwork without the approval of Scania. If anyother equipment other than the factory fitted

equipment is connected, safety and reliabilitycan be affected.

Note:It is not possible to measure or checkCAN messages with a multimeter either. Use thefault codes to locate the cause of any possiblemalfunctions.

CAN is an abbreviation of Controller AreaNetwork. CAN communication is used to reducethe number of cables in the vehicle and at thesame time increase reliability. Thecommunication circuit consists of two cables,CAN H (High) and CAN L (Low).

Several different systems are connected to thesetwo cables and in this way form a network.CAN communication is used for examplebetween EDC, ABS/TC, EBS, the retarder,Opticruise and the coordinator.

In simple terms, CAN communication is ratherlike radio. The data messages that travel along aCAN cable can be compared to radio waves thattravel through the air.

When listening to the radio, the receiver is set sothat one radio station is heard at one time. Onlyone station is heard, even though many otherradio stations are transmitting simultaneously.

A control unit does approximately the same withthe messages that travel through a CAN cable. Itlistens, for example, for information from theEDC control unit concerning the coolanttemperature, receives this value and uses it in itscalculations.

The control unit receives several CAN messages- which are sent through the communications

EDCABS/TC

OPTICRUISE

COO EBS

116

757

circuit - in a special memory. This memory maybe compared to a number of radio receivers thatare all on but set to different radio stations tolisten to several radio programmessimultaneously. In this way, the control unitcontinuously senses what is happening.



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sistema de combustible con inyector bomba pde y edc s6. descripción de funcionamiento

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