Aftersales Training - Product Information. MSA automatic ... Automatic Engine Stop and … · BMW...

BMW Service

Aftersales Training -Product Information.MSA automatic enginestop and start.

The information contained in the Product Information and the Workbook form an integral part ofthe training literature of BMW Aftersales Training.

Refer to the latest relevant BMW Service information for any changes/supplements to theTechnical Data.

Information status: June 2006

Contact: [email protected]

© 2006 BMW AGMünchen, GermanyReprints of this publication or its parts require the written approval ofBMW AG, MünchenVS-12 Aftersales Training

Product Information.MSA automatic engine stop andstart.

Efficient environmental protection withBMW

MSA - a DME/DDE function

DC/DC converter for even power supply

Notes on this Product Information

Symbols used

The following symbols are used in this Product Information to facilitatebetter comprehension and to draw attention to important information.

3 contains information to facilitate better understanding of thedescribed systems and their function.

1 identifies the end of a note.

Information status and national variants

BMW vehicles conform to the highest safety and quality standards.Changes in terms of environmental protection, customer benefits anddesign render necessary continuous development of systems andcomponents. Consequently, this may result in differences between thisProduct Information and the vehicles available in the training course.

Unless stated otherwise, this document describes left-hand drive vehicleswith European specifications. On right-hand drive vehicles, some controlsor components are arranged differently from the illustrations in thisProduct Information. Further differences may arise as the result of theequipment variants used in specific markets or countries.

Additional sources of information

Further information on the individual subjects can be found in thefollowing:

- Owner's Handbook

- BMW diagnosis system

- Workshop systems documentation

- SBT BMW Service Technology.

Contents.MSA automatic enginestop and start.

System overview 1

Introduction 1Input/output diagram 2System circuit diagram 4

Functions 7

Preconditions 7Basic functions 8Stop inhibitors and start compellers 9System-related deactivation 13Deactivation by MSA button 16Energy management 17

System components 19

Components of MSA 19Actuators 24Indication concept 26Integration of measure for stabilizing electricalsystem 27

Service information 33

Notes for service staff 33

Summary 35

Points to remember 35

5

System overview.MSA automatic engine stop and start.

Introduction

The automatic engine stop and start function(MSA) is one of the measures aimed atmeeting the ACEA voluntary commitment, towhich BMW subscribes, of reducing CO2emissions by 2008. It lowers fuel consumptionby automatically switching the engine offwhen the car is stationary. The engine issubsequently restarted automatically as well,as soon as the appropriate conditions forrestarting are satisfied.

MSA is being introduced on the E8x, E9x andR5x models in conjunction with manualtransmission and four-cylinder engines.

On those models, MSA will be standardequipment. The option SA1CC can also beordered for controlling MSA.

The MSA function is integrated in the enginemanagement (DME/DDE). The MSA functionmakes use of a variety of existing data from thebus system. New sensors are also required forproper functioning of the system. The input/output diagram below provides a general viewof the most important input and output signals.

1

5

Input/output diagram

1 - Input output diagram for automatic engine stop and start

2

5

Index Explanation Index Explanation

1 Digital (petrol) engine managementmodule (DME)/Digital diesel engine managementmodule (DDE)

8 Bonnet switch

2 Car access system 9 Seatbelt-buckle switch

3 Starter 10 Clutch switch, 90 % position

4 Instrument cluster 11 Clutch switch, 10 % position

5 Centre console switch cluster withMSA button

12 Brake servo vacuum sensor

6 Wheel speed sensor 13 Gearbox neutral position sensor

7 Intelligent battery sensor (IBS) 14 Automatic climate control (IHKA)/Climate control (IHKR)

3

5

System circuit diagram

2 - System circuit diagram for automatic engine stop and start

4

5


1 Bonnet switch 8 Intelligent battery sensor (IBS)

2 Starter 9 Centre console switch clusterwith MSA button

3 Brake servo vacuum sensor 10 Automatic climate control

4 Gearbox neutral position sensor 11 Instrument cluster

5 Digital (petrol) enginemanagement module (DME)/Digital diesel enginemanagement module (DDE)

12 Car access system

6 DC/DC converter 13 Clutch switch

7 Junction box (control unit withpower distribution box)

5

5

K-CAN signals at the DME/DDE

In/Out Signal Source/Recipient Function

In Gearbox neutral position > Neutral position sensor> DME/DDE

Stop inhibitor andstart inhibitor

In Brake servo vacuum > Brake servo vacuum sensor> DME/DDE

Stop inhibitor andstart compeller

In Bonnet open/closed > Bonnet microswitch> CAS

MSA deactivation

In Change of steering angle > Steering-angle sensor> EPS/AL

Stop inhibitor

In Clutch pedal position10%

> Clutch switch> DME/DDE

Start compeller whenin neutral, stopinhibitor

In Clutch pedal 90 %position

> Clutch switch> CAS

Start compeller whenin extended neutralzone, stop inhibitor

In Driver's seatbeltfastened/unfastened

>Seatbelt-buckle switch> ACSM

MSA deactivation

In MSA on/off >>MSA button on centre consoleswitch cluster> IHKA

MSA activation/deactivation

In Battery status > IBS> DME/DDE


In Road speed >Wheel speed sensor> DSC


In Evaporator temperature > Evaporator temperature sensor> IHKA/IHKR


In Degree of misting > Misting sensor> IHKA


Out Display > DME/DDE> Instrument cluster

Status indicationsand CC messages

Out Start signal > CAS> starter motor

Engine starting

6

6

Functions.MSA automatic engine stop and start.

Preconditions

The MSA function can only be performedunder certain conditions.

The engine is switched off if

• the vehicle is stationary (speed below 3 kph)

• the vehicle has been driven at over >5 kphsince the last time the engine was stopped

• the vehicle has been driven at over >5 kphsince the last time terminal 15 wasswitched over

• the manual gearbox is in neutral

• the clutch pedal is not depressed

• the steering wheel is not being turned

• the engine speed is approximately idlingspeed

The engine is restarted in response to driveraction if

• the gearbox is in neutral (see section onneutral position sensor) and the clutchpedal is depressed (10 %)

• the gear lever is in the extended neutralzone (see section on neutral positionsensor) and the clutch pedal is depressed(90 %)

3 The engine is restarted without action bythe driver (applies only if switched off by MSA,i.e. not if switched off by SST for instance) if

• the vehicle starts rolling (5 kph forwards orbackwards)

• the brake system pressure falls below adefined threshold

• the battery charge level falls below adefined threshold

• the misting sensor detects misting on thewindscreen (IHKA)

• the evaporator temperature exceeds acertain threshold while the air-conditioningcompressor is switched on

1

The basic condition for restarting the engine isthat the manual gearbox is in neutral.

A precise description of all the conditions andexceptions that determine whether or not theMSA can operate is provided in the section"Stop inhibitors and start compellers".

3 External conditions such as the outsidetemperature (MSA only operates attemperatures ≤ +3 °C) can result in the MSAfunction being unavailable for extendedperiods. 1

The MSA function is always activated whenthe engine is not running, terminal 15 isswitched on and a so-called "driving cycle" isinitiated. The MSA can be switched off bymeans of the MSA button. The MSA isautomatically switched on again the next timea driving cycle is initiated.

7

6

Basic functions

Provided all the preconditions are satisfied, the MSA functions as follows:

Vehicle is moving ... Gear is engaged ...

Accelerator is depressed ...

Engine is running ...

Instrument cluster shows timeand temperature.

Driver brakes until vehiclecomes to a halt ...

Driver puts the gearbox inneutral ...

... and releases the clutchpedal ...

Engine stops ...

The instrument cluster showsthe "Stop/Start" symbol.

Driver wants to move off again...

Driver depresses the clutchpedal ...

Engine starts ...

The appropriate gear can beengaged and the car canmove off.

The "Stop/Start" symboldisappears and time andtemperature reappear ...

8

6

Stop inhibitors and start compellers

The MSA function has to be suppressedunder certain conditions. The engine thencontinues running even though the gear lever

is in the neutral position and the clutch pedalhas been fully released.

Example: stop inhibitor

Conversely, there are also situations in whichthe engine must be started even though thedriver takes no active steps (e.g. pressing theStart/Stop button or depressing the clutch).

3 Point out the possible start compellers (=conditions requiring engine starting withoutaction by driver) if customers enquire. 1

The following are possible stop inhibitors andstart compellers:

• Engine conditioning (stop inhibitor only)

• Battery status

• Electrical system power demand

• Climate control requirements

• Inadequate brake servo vacuum

• Inadequate power steering assistance (stopinhibitor only)

• Various safety requirements (reverse gearengaged, steering wheel movement ->deceleration)

• Vehicle starting to roll

Engine conditioningIn addition to its primary function, that ofproviding the motive power for the vehicle, theengine also has to perform a number ofancillary functions. Those ancillary functionsare necessary for operational reliability,comfort/convenience functions and exhaustemissions compliance.

The following conditions prevent the enginebeing switched off:

• Engine-coolant temperature below acertain level (dependent on engine model,approx. 20 - 50 °C)

• Activated charcoal filter must have beenflushed

• Engine not running at idling speedi.e. > 900 rpm.




Engine continues running ...

A stop inhibitor is present andthe instrument clusterdisplays the appropriatesymbol.

9

6

Battery statusThe battery status is a fundamental factoraffecting the existence of stop-inhibiting andstart-compelling conditions. Computation ofthe battery status is performed by theAdvanced Power Management (APM). Thatfunction is integrated in the enginemanagement (see Energy management) andhas been extended specifically for the MSA.

The aim is to ensure reliable engine startingfrom an electrical system viewpoint after theengine has not been running for a definedperiod. Before the engine is switched off, areliable prediction of the minimum absoluteremaining usable capacity and the minimumvoltage level when subsequently restarting theengine from warm is made. The APMcomputes the status of the electrical systemon the basis of the following data:

• Battery status

– Charge level too low

– Charge level implausible

– Battery temperature too high

– Starting voltage dip too low on previousMSA start

• Power demand from electrical equipment inuse

The result can be either prevention orrequirement of MSA function. The followinginformation may be signalled:

• Stop-inhibiting condition

• Start-compelling condition

The MSA responds to battery charge level inthe following manner:

3 If the battery charge level drops into thered zone after the MSA has switched theengine off, the MSA restarts the engine. 1

Alternator capacity utilizationReduced alternator output capacity or a highlevel of power demand from the electricalsystem (I > 60 A) as an average immediatelybefore the point at which the engine would be

switched off and which can/must not bereduced or switched off by the APM results ina stop inhibitor.

Index Explanation

1 In the green zone, the MSA canfunction fully

2 In the yellow zone, the engine isnot switched off

3 In the red zone, the engine isstarted

10

6

Climate control requirements

Heating mode

If the engine coolant temperature issignificantly below the required temperaturefor heater fan operation it is treated as a stopinhibitor. In heating mode while the engine isnot running, the electric auxiliary water pump(N47) or main electric water pump (N43) isactivated. The demand is signalled by theclimate control panel via the bus system.

Air-conditioning mode

In certain situations it is necessary to ensurethat the air conditioning compressorcontinues to provide cooling capacity so as todehumidify the vehicle interior and lower thetemperature. The following stop inhibitorsmay be brought to bear:

• Automatic air conditioning: MAX AC buttonpressed

• Air conditioning: high fan setting and low fanoutput temperature and compressor buttonpressed.

The MSA has to be inhibited if there is ademand for windscreen defrosting. This isdetected by:

• Automatic air conditioning: Defrost buttonpressed and compressor activated

• Air conditioning: high fan setting and air flowdirected onto windscreen and compressoractivated

If the misting sensor signal indicates that thewindscreen is misting, MSA is inhibited if theair conditioning is switched on (stop-inhibitingcondition). If this occurs when the engine isswitched off, a start demand is issued.

If the evaporator temperature rises above adefined threshold when the engine has beenswitched off by the MSA and the airconditioning is on, this constitutes a start-compelling condition.

3 The engine may be started without anyaction by the driver (pressing the Start/Stopbutton or depressing the clutch pedal).

If the evaporator temperature is above adefined threshold when the air conditioning ison, this constitutes a stop-inhibiting or start-compelling condition.

If the engine has been switched off by theMSA, a less comfortable interior climate mayresult (dampness/odour). 1

Inadequate brake servo vacuumIn order to ensure there is always sufficientbraking power (even when the engine isswitched off) the vacuum in the brake servohas to be continuously monitored. If required,

the engine is automatically restarted, i.e. if thevacuum drops below 500 hPa while theengine has been stopped by MSA.

Power steeringThe engine can not be switched off as long asthe steering wheel is being turned. In suchsituations, there must always be powersteering assistance available. Only when theMSA does not detect steering wheel

movement on the basis of the signals from thesteering column switch cluster can the enginebe switched off. The information is providedvia the bus system.

11

6

Safety requirements

Preventing automatic engine startingwhen work is being carried out in theengine compartment

If the bonnet is opened, the MSA isdeactivated in order to prevent the enginebeing started automatically when work isbeing carried out in the engine compartment.

It is always possible to start the engine with theStart/Stop button.

Reactivation of the MSA is possible once thebonnet has been closed and either the enginehas been started or the vehicle speed hasreached 5 kph.

Preventing automatic engine starting ifthe driver has left the vehicle

If the driver gets out of the vehicle, the MSA isdeactivated in order to prevent the enginebeing started automatically.

The driver's seatbelt buckle is monitored forthat purpose.

• If the driver's seatbelt buckle is unfastened,the MSA is deactivated. The engine can notbe switched off by the MSA until theseatbelt buckle is fastened again and thevehicle has reached a speed of > 5 kphonce (stop inhibitor only). Caution: theengine can be started despite the seatbeltbeing unfastened and the bonnet beingopen if the vehicle speed exceeds 5 kph.

• If an automatic start demand is issued, a CCmessage is generated.

• Reactivation of the MSA is possible oncethe driver's seatbelt has been fastened andeither the engine has been started or thevehicle speed has reached 5 kph.

The signal indicating the status of theseatbelt-buckle switch is provided by thesafety system via the bus system.

Preventing the engine being switched offif the vehicle is moving

On no account must the engine be switchedoff if the vehicle is moving. The engine can notbe switched off until the vehicle speed isbelow 3 kph.

Preventing automatic engine startingwhen the drive is engaged

If the drive is engaged on a vehicle with manualtransmission, automatic engine starting mustbe prevented.

Detection of when the drive is disengaged isperformed by means of the gearbox neutralposition sensor.

12

6

System-related deactivation

The MSA can also be deactivated for system-related reasons. A CC message is displayed tothe driver on the instrument cluster if a startrequest is received.

The following deactivators can be responsiblefor system-related deactivation:

• Seatbelt-buckle signal

• Bonnet switch

• Engine emergency mode

• Implausible sensor or bus signals

• Vehicle being towed

• Key not detected (Comfort Access)

Response to deactivation by a safety functionIf the MSA is deactivated by a safety functionafter the engine has been switched off by theMSA, the engine can only be restarted by the

Start/Stop button and if the road speedexceeds5 kph.




Engine stops ...

Driver unfastens seatbelt ...

The MSA function isdeactivated, the engineremains off ...

The engine only restarts if thedriver presses the Start/Stopbutton.

13

6

Response to deactivation by system faults (emergency modeconcept)If a fault in the MSA system complex (signalinputs, actuator systems, bus signals ...) isdetected, a stop inhibitor is set or the MSAdeactivated.

Thus, detection of a fault while the engine isrunning prevents the MSA subsequentlyswitching the engine off at any time. If theengine detects a fault after it has beenswitched off by the MSA, the followingscenarios are distinguished:

1. If a safety-related fault is detected (faulton neutral-position sensor, brake servovacuum sensor, clutch sensor, enablesignal line, bonnet switch or driver'sseatbelt-buckle switch), the MSA is

immediately deactivated and automaticrestarting of the engine is no longerpossible.

2. If other types of fault are detected (DME/DDE emergency mode, etc.) which arenot safety-critical, the MSA is allowed tostart the engine once more.Subsequently, however, the MSA is nolonger permitted to switch the engine off.

3. If faults in bus communication with theDME/DDE engine management moduleare encountered, the MSA is deactivated.

Deactivation due to external conditions

If the MSA is deactivated due to a system fault, the instrument clusterdisplays a CC message (ID397).

Instruction as to further action required (take car to dealer) ID397.

If the seatbelt is unfastened or the bonnet opened after the enginehas been switched off by the MSA, the MSA is deactivated and theengine can only be restarted by the Start/Stop button or if the roadspeed exceeds 5 kph. If the driver attempts to start the car bydepressing the clutch, CC message ID450 is displayed after 1-2seconds.

14

6

Signal path in electrical systemThe Car Access System (CAS) is only asubordinate control unit in this situation anddoes not perform any calculations of its ownfor clearing engine starting.

The information for engine starting clearanceis transmitted via the bus system in the firstinstance:

• DME/DDE

• PT-CAN

• Junction-box ECU

• K-CAN

• CAS.

In addition, clearance for starting is alsosignalled via a separate line. The CAScompares the two signals. If the time lagbetween the two signals exceeds a certainlimit, the MSA is not allowed to start theengine. A fault memory entry is registered.

1 -

15

6

Deactivation by MSA button

The MSA function can be manuallydeactivated by means of the MSA button, inwhich case the LED in the button lights up.

Every time the engine is restarted, the MSAfunction is reactivated.

Button not pressed

-> LED off

Button pressed; driver wants MSAdeactivated

-> LED on




Engine continues running ...

16

6

Energy management

Availability when engine switched off by MSAWhen the engine has been switched off by theMSA, excessive power consumption must beavoided. Therefore, all large consumers ofelectricity are switched off, or theirconsumption reduced. The displays remainactive.

The following are switched off:

• Rear window heater

• Mirror heaters

• Seat heaters

The following are adjusted to the situation:

• Heater fan

The automatic climate control (IHKA) isresponsible for adjusting the heater fan.

Availability while engine is started by MSAThere are restrictions to the followingfunctions while the engine is being started bythe MSA: After the engine has been started,automatic sequences are continued.

• Power windows

• Windscreen wipers

• Sliding sunroof

• Interior and exterior lights

If the power windows or sunroof are in themiddle of an automatic sequence when theengine is started, the sequence is interrupted.Once the engine has been started, theautomatic sequence is continued.

The windscreen wipers are also briefly haltedwhile the engine is started.

The following functions are not restricted inany way:

Playback of:

• discs

• radio

• TV

17

7

System components.MSA automatic engine stop and start.

Components of MSA

As already set out in the system overview, theMSA function involves a complex system ofinteractions across the entire bus system.However, the information required is providedby existing signals from other systems.

The following components are necessary forthe MSA:

• System's own sensors

– Brake servo vacuum sensor

– Manual gearbox neutral position sensor

– MSA button

• External sensors, e.g.

– Clutch switch

– Bonnet switch

– Seatbelt-buckle switch (driver)

Brake servo vacuum sensor

In order to ensure that there is sufficientvacuum for brake servo assistance at all times,the brake servo is fitted with a vacuum sensor.

The brake servo vacuum sensor is locatednext to the brake servo and is connected via aseparate lead.

The brake servo vacuum sensor suppliesvoltage signals proportional to the vacuumpresent (see graph).

3 If there is insufficient vacuum, the MSAstarts the engine even without action by thedriver. 1

1 - Vacuum sensor

2 - Voltage proportional to vacuum

19

7

20

Manual gearbox neutral position sensorThe neutral position sensor is mounted on topof the gearbox housing and its purpose is todetect when the gear lever is in the neutralposition. The neutral position sensor is aPLCD (permanent-magnet linear contactlessdisplacement) sensor.

Moving the gear lever moves the gear-shiftlinkage rod and, therefore, the magnet. TheDME/DDE is able to detect the position of thegear lever by means of the PLCD sensor.

The following distinctions have to be made forthe purposes of the MSA function:

• Gear engaged - MSA function disabled

• Gear lever in neutral position - MSA startsengine if clutch is depressed by 10 %

• Gear lever moved slightly out of neutralposition - engine is started if clutchdepressed by 90 %

3 - Manual gearbox neutral position sensor

4 - Method of operation ofneutral position sensor


1 Digital (petrol) enginemanagement module (DME)/Digital diesel enginemanagement module (DDE)

3 Magnet

2 PLCD sensor 4 Gear-shift linkage rod

5 -

Index Explanation

1 PLCD sensor learning zone

2 Engine started if clutchdepressed by 10 %

3 Engine started if clutchdepressed by 90 %

7

The learning sequence (orange) is necessaryto compensate for tolerances in themechanical and electrical systems.

The DME/DDE then calculates the maximumranges relative to the learned gear-leverneutral position within which the engine canbe started if the clutch is depressed.

When the clutch is fully depressed, the enginecan still be started when the gear lever isdeflected by up to 1.89 mm (10 % PWM).

The PLCD sensor is provided with a 5 V powersupply. The output voltage is a PWM signal

whose pulse duty factor changes according tothe position of the gear lever (10...90 %).

The neutral position sensor has to complete alearning phase. If the DME/DDE is replaced,the learned data can be copied by reading thelearned position using the diagnosis system(provided the old DME/DDE can be read)before the unit is replaced and then writing itto the new unit.

The learning sequence is described in theBMW diagnosis system.

MSA buttonThe MSA button can be used to deactivatethe MSA system. If the terminal 15 signalchanges to on when the engine is not running

or if the MSA button is pressed again, theMSA is reactivated.

The signal from the MSA button is received bythe IHKA and passed on to the enginemanagement.

The indicator lamp is controlled by the IHKA.

6 - MSA button

21

7

Clutch switch

The existing clutch switch signal is used as aninput variable for the MSA.

Two statuses are registered:

• 10 % clutch pedal depression

• 90 % clutch pedal depression

7 - Clutch switch


1 10 % clutch pedal depressiondetected

2 90 % clutch pedal depressiondetected

22

7

Bonnet switchThe bonnet switch signal is taken into accountas a determining factor in the MSAcalculations. If the bonnet is open, the enginemust not be started or stopped by the MSA forsafety reasons.

3 If the bonnet switch is defective(continuously signals "open"), all MSAfunctions are suppressed. 1

3 If the top of the bonnet switch is coveredover (workshop mode), it signals "Switchclosed". The MSA function is active. Caution:the engine may be started automatically. 1

Seatbelt-buckle switchThe seatbelt-buckle switch enables the MSAto detect if the driver's seatbelt is fastened. Ifthe driver's seatbelt is not fastened, the MSAresponds in different ways depending on thevehicle status.

• If the engine is running, a stop inhibitor isset

• If the engine has been switched off by theMSA, the MSA is deactivated. The enginecan only be restarted by means of the Start/Stop button.

8 - Bonnet switch

9 - Seatbelt-buckle switch

23

7

Actuators

The MSA indirectly operates the starter motorand indicator lamps/CC or display messageson the instrument cluster.

Starter

With the MSA, the starter motor hassignificantly more work to do. Therefore, it hasbeen dimensioned for substantially more(approx. 8 times as many) starting cycles.

The components of the starter motor havebeen adapted to the higher demands (seekey).

10 - Starter


1 Forked lever: reinforced,armoured

6 Planetary gears: more directtransmission

2 Relay armature: lubricant coated 7 Planetary gears: needle rollerbearings

3 Relay springs: greater number ofcycles

8 Planetary gears: sintered internalgear with damper

4 Starter motor (+electricalsystem): uprated, higher power

9 Pinion: number of teethincreased

5 Magnets: higher flux/demagnetization resistance (hightorque)

10 Drive shaft bearing: needle rollerbearing

24

7

Indicator lampThere are a number of new indications thatprovide feedback from the MSA for the driver.

The possible MSA indications are detailed inthe next chapter.

AlternatorDue to battery discharge while the engine hasbeen switched off by the MSA, a morepowerful alternator is fitted.

BatteryThe MSA always comes together withintelligent alternator control (IGR). Due to thesubstantially more frequent charging anddischarging cycles, the load on the battery isvery high. AGM batteries provide thepossibility of achieving a similar service lifedespite the high loadings because they have ahigher recharging capacity.

On the E87 and E90, AGM batteries with acapacity of 80 Ah or 90 Ah are fitted,depending on equipment levels.

11 - Indicator lamp

12 - Alternator

13 - Battery

25

7

Indication concept

The following indications are used inconjunction with the MSA:

If the engine can be started by the MSA, that status iscontinuously indicated on the instrument cluster. If the driverwants to see the time and temperature, the indication can besuppressed by pressing the computer roller.

If there is a fault on the MSA hardware that causes the MSA to bedeactivated, a CC message is displayed.

Text of CC message: "Automatic stop/start has failed."

ID397

If the MSA is deactivated to ensure functional safety ("Seatbeltbuckle unfastened"), another CC message is displayed as soonas a start compeller is present:

Text: "Automatic stop/start deactivated."

ID450

26

7

Integration of measure for stabilizing electrical system

As a result of the substantially more frequentstarting cycles, there are correspondinglymore voltage dips in the electrical system dueto the electrical load.

In order to stabilize the supply voltage forparticularly voltage-sensitive electricalcomponents and thereby protect them, a DC/DC converter is used in conjunction with theMSA.

The DC/DC converter supplies the terminal30g_DC/DC and terminal 30g_f_DC/DC relayswith a constant voltage even during a startingcycle.

The DC/DC converter requires the followingcontrol signals:

• Terminal 50

• Terminal 15

• Terminal 30g

• Terminal 30g_f ON

• Terminal 30g_f OFF

The terminal 50 signal is provided by the CAS,the terminal 15 and terminal 30g signals bythe junction-box ECU.

The DC/DC converter has a diagnosis output(PWM signal) that provides the followingcoded information:

• Converter OK

• Converter defective

• Converter overheated

The diagnosis lead is read and analysed by theJB.

LocationThe DC/DC control unit is in the electronicsbox in the engine compartment.

DesignThe DC/DC control unit contains theelectronic circuitry for converting the voltageand the terminal 30g_f_DC/DC and terminal30g_DC/DC relays.

27

7

System circuit diagram for DC/DC converter

In addition to terminals 30g_DC/DC and30g_f_DC/DC, the terminals 30g and 30g_f,and therefore the terminal relays, are retained.

14 - System circuit diagram for DC/DC converter


1 Car access system 3 Junction-box ECU

2 DC/DC control unit 4 Junction-box power distributor

28

7

Terminal managementVoltage-sensitive electrical components aresupplied with a matched voltage whennecessary. That supply is only provided undercertain conditions (starting cycle and voltage

below 10.5 V). Otherwise, the connectedcontrol units are supplied with the normalelectrical system power supply divertedthrough the DC/DC converter.

15 - Terminal management


1 Electrical system power supplyunder various loads before DC/DC converter

4 DC/DC control unit

2 DC/DC converter 5 Junction-box power distributor

3 Electrical system power supplyunder various loads after DC/DCconverter

29

7

DC/DC control unitInside the DC/DC converter is the actualconverter module that, depending onconditions, provides either a matched voltage

or the normal electrical system power supplyvoltage for the terminals 30g_DC/DC and30g_f_DC/DC.

The DC/DC module uses the input voltagetesting leads and terminal 50 to decidewhether to supply the DC/DC terminals via thebypass or the DC/DC converter.

The relays 30g_DC/DC and 30g_f_DC/DC arealso accommodated in the DC/DC control unit.

The terminal 30g and terminal 30g_f relays areretained in the power distributor.

The DC/DC control unit basically operates inthe following modes:

• Boost mode

• Bypass mode

16 - DC/DC control unit


1 Bypass switch 6 Input voltage subject to electricalsystem fluctuations

2 DC/DC module 7 Input voltage testing leads

3 Diagnosis lead 8 Terminal 50 data lead

4 DC/DC converter 9 DC/DC module power supply

5 Stabilized electrical systemvoltage

30

7

Bypass modeIn bypass mode, the electrical system powersupply is not fed through the DC/DC

converter. A bypass passes it straight throughto the outputs of the DC/DC converter.

Boost modeIn boost mode, the electrical system voltage isadjusted. The decision as to when stabilizationis necessary/possible is dependent on thefollowing factors:

• Terminal 50 on/off

• and input voltage at the DC/DC converter.

Terminal 50Boost mode is activated if terminal 50 is onand the voltage drops below 10.5 V. As soonas terminal 50 is active, the DC/DC convertergoes into a standby mode in order to improveresponse characteristics. Not until the voltagedrops below the defined threshold of 10.5 V isboost mode activated and the matchedvoltage supplied to the terminal 30g and 30g_frelays.

The blue line represents a typical voltageprogression when the engine is started.Depending on external factors, the voltagemay drop as low as 7.5 V.

The red line shows the voltage provided by theDC/DC control unit.

17 - Typical voltageprogression when engineis started

31

8

Service information.MSA automatic engine stop and start.

Notes for service staff

3 The MSA only operates under certainconditions (see Functions/Preconditions). Ifcomplaints are received from customers,those conditions must always be checked. 1

3 If the top of the bonnet switch is coveredover (workshop mode), it signals "Switchclosed". The MSA function is active. Caution:the engine may be started automatically. 1

3 The MSA relies on information from theenergy management system. If the battery isreplaced, or any time the unit is flashprogrammed, reference data relating to thecharge level and health of the battery may belost.

Only after a learning period of approx. 6 hours(bus system must be in sleep mode) is thatdata available again. During that learningphase, he MSA cannot be activated forreasons of reliability. 1

3 If MSA system faults are registered, theautomatic engine stop start function isdeactivated on principle (before making anyreplacements, it is essential that sensormalfunction is established by a functioncheck). 1

3 After any work on a vehicle with MSA thatinvolves any of the following operations, theMSA function is deactivated until the newquiescent current/battery parameters havebeen learned. The MSA reactivates itselfautomatically. Customers should be madeaware of this.

• Disconnection of the battery

• Programming of the engine management(not in all cases).

1

3 Always follow the appropriate safetyprecautions when working on cars with MSA!

Always make sure that the MSA function isswitched off before carrying out any hands-onwork on the engine in order to prevent theengine being switched on automatically whenworking in the engine compartment! (Functionis disabled by: deactivating by MSA button/seatbelt unfastened and driver's door open/bonnet open.)

Handling safety risks: in most test modulesthat do not test the MSA function but ratherindividual component functions and/or leads,the MSA function is switched off for safetyreasons until the next change of terminalsignal. This is done automatically, i.e. a routinethat temporarily deactivates the MSA isexecuted without the Service technicianhaving any control over it.Background: under certain conditions and inthe worst-case scenario, i.e. if the seatbelt-buckle switch/bonnet switch/MSA button isdefective, the MSA is not automaticallydeactivated. If the Service technician carriesout work in the engine compartment, thiscould, under certain circumstances, result inthe engine starting automatically -> impendingdanger.

This is as follows:

"Note: Always follow the appropriate safetyprecautions when working on cars with MSA!

Always make sure that the MSA function isswitched off before carrying out any hands-onwork on the engine in order to prevent theengine being switched on automatically whenworking in the engine compartment! (Functionis disabled by: deactivating by MSA button/seatbelt unfastened and driver's door open/bonnet open.)

To continue ... press right arrow."

Safe mode is now activated. You can continuewith the test module.

To continue ... press right arrow."

This Service information can befound in the introduction, the systemoverview and the systemcomponents section.

33

8

OR

Safe mode could not be successfullyactivated. Continuation of work is forbidden forsafety reasons!

Test module terminated. Continue testingsequence." 1

3 The tester diagnoses cover the followingcomponents:

• Neutral position sensor

• Brake servo vacuum sensor

• Both clutch switches

• MSA button

• Power management relevant to MSA

• DC/DC converter relevant to MSA in CAS.

There are also three Service functions forchecking the software functionalities.

Additional points:

• Diagnoses for the following units involved inthe MSA system complex: wheel speedsensor, instrument cluster, battery and IGR,power management, Junction box, IHx,CAS, DME/DDE and seatbelt buckle cannotbe entirely covered by MSA diagnoses. Therelevant system diagnoses should be usedin those cases.

• Diagnosis cannot be performed on thebonnet switch and therefore it cannot berepresented on the tester.

3 Signal testing:

There are two new testing adaptors availablefor testing the signals of the two new sensors:

• Adapter for X88 (neutral position sensor)

• Adapter for X126 (brake servo vacuumsensor) BA

1

ExamplesBefore carrying out a diagnosis or replacingcomponents it is essential to have a detaileddiscussion with the customer.

Customer says: "My engine has not (or onlyrarely) switched off in recent weeks despitebeing stationary for long periods."

You ask: How high was the outsidetemperature? Is the battery in good condition?

Customer says: "My engine starts up of itsown accord while the car is stationary."

You explain: The engine can be startedautomatically by the MSA under the followingconditions:

• If the brake servo vacuum is too low

• If the battery charge is too low

• If the evaporator temperature is too high

• If the windscreen is misting too much

Customer says: "The radio switches offwhile the engine is being started."

You explain: The DC/DC control unit isresponsible for voltage stabilization for theentertainment system. We should do a systemcheck. The faults are stored in the junction-box ECU memory.

Customer says: "When I get out of the car aCC message appears."

You ask: Is the customer using the MSA stopfunction when leaving the car (e.g. parking inthe garage)?

When the seatbelt is unfastened, a CCmessage is generated because the MSAassumes that the journey is going to becontinued.

34

9

Summary.MSA automatic engine stop and start.

Points to remember

The table below summarizes the mostimportant information on the subject of theautomatic engine stop and start function.

The list outlines the main points in conciseform and provides the opportunity forrechecking the most important facts providedin this Product Information.

Information on everyday theoreticaland practical applications.

Preconditions

The MSA function can only be performed under certain conditions.

The engine is switched off if:

• the vehicle is stationary (speed < 3 kph)

• the vehicle has been driven at over >5 kph since the last time theengine was stopped

• the vehicle has been driven at over >5 kph since the last timeterminal 15 was switched over

• the manual gearbox is in neutral

• the clutch pedal is not depressed

The engine is restarted in response to driver action if:

• the gearbox is in neutral (see section on neutral position sensor) andthe clutch pedal is depressed (10 %)

• the gear lever is in the extended neutral zone (see section on neutralposition sensor) and the clutch pedal is depressed (90 %)

The MSA function is only active at an outside temperature of at least+3 °C and no more than +30 °C (if air conditioning is on) while thesteering wheel is not moving and the engine is running roughly at idlingspeed

Gearbox neutral position sensor

The gearbox neutral position sensor and brake servo vacuum sensorare new and only required in conjunction with the MSA for systemcontrol purposes.

35

9

DC/DC converter

The DC/DC converter stabilizes the power supply voltage for voltage-sensitive electrical equipment during the engine starting cycle.

36

Dieser Text muss hier stehen, damit die Seite vom API-Client nicht gelöscht wird.Dieser Text ist notwendig, damit die Seite nicht quergestellt wird.!

Bayerische Motorenwerke AktiengesellschaftBMW Group TrainingsakademieAftersales TrainingRöntgenstraße 785716 UnterschleißheimGermany

:

Aftersales Training - Product Information. MSA automatic ... Automatic Engine Stop and … · BMW...

Documents

Transcript of Aftersales Training - Product Information. MSA automatic ... Automatic Engine Stop and … · BMW...