Sequential M Transmission M5, M6

23 01 04 (088) Sequential M transmission E60/M5/E63/M6





Introduction
The new BMW M5 is the first car in the world to feature the sequential M transmission with 7 forward gears and 11 driving programs (5 driving programs in automatic mode and 6 driving programs in manual mode).

The sequential M transmission is derived from the world of motor racing. The sequential M transmission has now been adapted for series production.
The sequential M transmission automates clutch operation and gear changes. An electrohydraulic control system takes over the clutch operation and gearshifts.
The sequential M transmission can be driven as follows in manual mode or in automatic mode:
- Sequential (manual mode) "S":
Gears are shifted by briefly pressing "+" or "-", as follows:
- Gear lever in the center console, or
- 2 gearshift paddles on the steering wheel
Gears may be skipped by briefly pressing several times quickly.
The shift pulse is transmitted electrically to the SMG control unit ("shift-by-wire", i.e. gear shift by electronics). With "shift-by-wire" there is no mechanical link between the gear lever or gearshift paddles and the transmission.
- Automatic mode "D":
In automatic mode, the gear shift times are automatically actuated according to maps and in response to the driving situation.
The 3rd generation of the sequential M transmission is a fundamentally new development.
Gear changes with this sequential M transmission are approx. 20 percent faster than with the 2nd generation. (In the ideal case, a gear change takes only approximately 65 milliseconds.)
The fast gear change is made possible by the installation of 4 shift rods:
- Shift rod R/1 (for reverse gear and the 1st gear)
- Shift rod 5/3 (for 5th and 3rd gears)
- Shift rod 6/7 (for 6th and 7th gears)
- Shift rod 2/4 (for 2nd and 4th gears)
Each shift rod is hydraulically selected by a shift cylinder. The shift cylinders are actuated by the SMG control unit.

The sequential M transmission is designed for torque up to 550 Newton meters and engine speeds up to 8500 rpm.
The key benefits of the sequential M transmission compared to conventional manual transmissions:
- No clutch pedal as the clutch is operated automatically.
- 2 operating modes can be selected:
- Sequential mode (manual mode) "S":
Sequential, manual gearshift via gear lever or gearshift paddles
- Automatic mode "D" ("Drive"):
Fully automated gear change
- "Drivelogic" makes a total of 11 driving programs available, which are used to adapt the shift characteristics of the sequential M transmission to the desired driving style.
- Short and precise gearshifts, faults are not possible when changing gear
- Safety and comfort: because the gearshift paddles are on the steering wheel, you can keep your hands on the steering wheel when you change gear.
Launch date:
09/04.

Brief description of components
The "sequential M transmission" system consists of the following components:

- Gear lever with gear lever cover
The gear lever allow gears to be changed by briefly pressing.
The gear lever has 6 gear lever positions:
- 3 engaging gear lever positions for neutral ("N"), reverse gear ("R") and manual mode ("o" symbol between "N" and "D/S")
- 3 one-touch positions for "+", "-", "D/S"
Gear indicator lighting is in the gear lever knob.
The following buttons are located in the gear lever cover: POWER, DSC, EDC and "Drivelogic".

- Steering wheel with 2 gearshift paddles
2 gearshift paddles are on the steering wheel.
Briefly pull the right gearshift paddle to shift up.
Briefly pull the left gearshift paddle to shift down.

- SMG control unit
The SMG control unit actuates the clutch operation and gear change. Furthermore, the SMG control unit sends messages to different control units, such as for adapting the engine speed.

- Hydraulic control unit
The hydraulic control unit performs the clutch operation and gear change electrohydraulically.
The hydraulic unit consists of the following components:
- Pressure accumulator
The pressure accumulator is fitted on the bottom left of the transmission. The pressure accumulator supplies enough hydraulic power for the gearshifts.
- Hydraulic pressure sensor
The hydraulic pressure sensor is fitted directly to the hydraulic block of the hydraulic control unit. The hydraulic pressure sensor reports the current hydraulic pressure to the SMG control unit. The hydraulic pump is switched on and off accordingly.
- Clutch slave cylinder with PLCD sensor
The clutch slave cylinder executes the clutch operations. The release travel is measured by the PLCD sensor (PLCD: Permanent magnetic Linear Contactless Displacement). The PLCD sensor is permanently linked to the clutch slave cylinder by a screwed connection.
The SMG control unit actuates the clutch slave cylinder via the solenoid valve for the clutch.
- Monitoring of the clutch position
During clutch action, the SMG control unit continuously measures and monitors the position of the clutch slave cylinder via the PLCD sensor. This also measures the clutch position.
In addition, the precise clutch slipping point is calculated from the different speeds of the engine and transmission.
- Clutch slipping point
The clutch slipping point is stored in the SMG control unit to ensure that clutch operation is optimized. The clutch slipping point is updated in the SMG control unit to take into account changes due to installation tolerances and wear.
- Solenoid valve for the clutch
The solenoid valve for the clutch is used for actuating the clutch slave cylinder.
- Hydraulic pump with electric motor
The hydraulic pump with electric motor builds up to 90 bar system pressure for the gearshifts. The hydraulic pump with electric motor is actuated via the SMG control unit.
- Hydraulic temperature sensor
The hydraulic temperature sensor measures the temperature of the hydraulic fluid at the hydraulic pump. The signal is used for actuation of the transmission functions in the SMG control unit. The signal is transmitted by a direct wire from the hydraulic temperature sensor to the SMG control unit.
- Pressure limiter valve
The pressure limiter valve prevent the oil pressure in the hydraulic control unit from becoming too high.
- Regulator block
The regulator block is installed in the center of the transmission housing close to the clutch housing.
The regulator block consists of the following components:
- 4 shift travel valves for actuating the hydraulic shift cylinders
- 2 pressure control valves for modulation of the shift force
- 4 hydraulic shift cylinders for moving the shift rod in the longitudinal axis
- 4 transmission position sensors for recording the selected gear
(The transmission position sensor for shift rod R/1 is designed as a double version.)
- Expansion tank
The expansion tank ensures that there is always sufficient hydraulic fluid available for the system.
- Check valve
The check valve at the outlet to the hydraulic pump prevents the hydraulic pressure from reducing when the hydraulic pump is inactive.
- Filter
A filter is installed at the inlet end of the hydraulic pump. The filter prevents impurities from entering the solenoid valve (functional failure). It is not necessary to clean the filter.
- Sensor for transmission input speed
The sensor (Hall sensor) measures the transmission input speed. The SMG control unit compares this speed with the engine speed. This is used to measure the clutch closing speed.
- Longitudinal acceleration sensor
Data from the longitudinal acceleration sensor has an effect upon the clutch function and the gearshift function (especially when pulling away on a slope). The longitudinal acceleration sensor is fitted to the floor panel under the front-passenger seat.
The following components and control units are involved in the function of the sequential M transmission:
- M-ASK / CCC and CID: Multi-audio system controller / Car Communication Computer and Central Information Display
- Multi-audio system controller / Car Communication Computer
The M-ASK / CCC is an interface for the instrument cluster to the Central Information Display (CID).
Additionally, the M-ASK / CCC emits acoustic warnings through the loudspeakers (depending on national version).
- Central Information Display
Amongst other things, the CID displays additional information about the Check-Control messages.
- Instrument cluster
The following displays are in the instrument cluster:
- Selected drive position:
- R (reverse)
- N (neutral)
- 1D...7D (automatic mode)
- 1...7 (manual mode)
- Selected driving program
- Check-Control symbol when there is a malfunction (on LCD display)
- Indicator lamp for "MDrive"
- HUD: Head-up display
The head-up display (option 610) shows the selected drive position.
- DME: Digital engine electronics
The DME sends messages about the current operating status of the engine to the SMG control unit (e.g. engine speed or torque).
The SMG control unit reports the current operating status of the transmission back to the DME.
- CAS: Car Access System
The CAS enables the starter only if a release signal is received from the SMG control unit (starter inhibitor).
The following conditions must be satisfied for the start to be enabled:
- The gear lever must be in position "N".
"N" must be on the instrument cluster LCD display. (This also keeps the transmission into "N").
- The SMG control unit enables the start when the brake pedal is depressed. The clutch is opened.
The CAS also provides input signals relating to terminal status (e.g. terminal 15 ON).
- SGM or KGM: Safety and gateway module or body gateway module
From 09/05, the vehicle electrical system has been modified. The KGM supersedes the SGM.
> SGM up to 09/05
The SGM is the gateway (= data interface) between:
- PT-CAN
- K-CAN
- Byteflight
The diagnosis wire is connected to the SGM.
> KGM from 09/05
The KGM is the gateway (= data interface) between:
- PT-CAN
- K-CAN
The diagnosis wire is connected to the KGM.
- LM: Light module
The reversing light is switched on upon the basis of messages from the SMG control unit to the light module.
- Brake light switch
The brake-light switch signal is used for the following operations:
- To release the shift lever lock (shift-lock)
- To detect a brake application
- To shift to "N" when the engine is shut-down
- For pulling away on a slope
Signal path: Brake light switch -> DME control unit -> PT-CAN -> SMG control unit
- FPM: Accelerator pedal module
The signal from the accelerator pedal module (driver's command) is needed to permanently monitor the vehicle's operating conditions (evaluation via DME).
- Parking brake warning switch
The SMG control unit uses the parking brake warning switch to detect whether the parking brake is applied or released. The signal is used for activating the clutch. The signal is transmitted by a direct wire from the parking brake warning switch to the SMG control unit.
- RLS: Rain-light sensor
The rain-light sensor is used for automatically adjusting the brightness of the gear indicator lighting in the gear lever knob to the background lighting.
- Bonnet contact switch
The 2 bonnet contact switches (Hall sensors) notify the SMG control unit of whether the bonnet is open or closed.
The gear is cancelled when the bonnet is open to prevent the vehicle from pulling away unintentionally in the workshop. (e.g. The engine is running at idle-speed. A drive position is selected. The accelerator pedal is in the idle position. The clutch is disengaged.
The accelerator pedal could be unintentionally pressed whilst work is being carried out in the engine compartment.)
The bonnet contact switches are permanently monitored whilst the vehicle is being driven. If a bonnet contact switch should fail, an "open bonnet" will detected when the vehicle is stationary. The gear indicator on the LCD display flashes.
The bonnet contact switches are fitted in the two bonnet locks.
- MDrive
Some settings may be preconfigured in the "MDrive" submenu of the iDrive. All of these settings are enabled when the button with the "M" symbol in the steering wheel is pressed (indicator lamp in the instrument cluster lights up).
The following functions are configured in advance for the sequential M transmission:
- Menu item "Sequential M transmission"
- Call up one of the 6 driving programs in manual mode
- Call up one of the 5 driving programs in automatic mode
- Local CAN
The SMG control unit and the digital engine electronics (DME) are connected via the local CAN. Information such as that needed for actuating the clutch (e.g. engine speed, engine torque) is transmitted over the local CAN.

System functions
The sequential M transmission comprised the following functions:

- Engine start
- Gearshift
- Drivelogic
- Driving in gear lever position "D" (automatic mode)
- Launch control (acceleration assist system)
- Slip detection
- Pulling away on a slope
- Vehicle standstill
- Gear lever position "Neutral" and ignition OFF
- Gear lever lock (shift-lock)
- Rock free, e.g. from snow
- Protection of valves
- Self-diagnosis during a pressure loss
- Emergency program



Engine start
To start the engine, the gear lever and transmission must both be in "N" (neutral) and the brake must be applied.
When the engine is started, sufficient system pressure must immediately be built up to open the clutch. This is why the SMG control unit is activated by the Car Access System (CAS) when the vehicle is unlocked. The SMG control unit measures the system pressure via the hydraulic pressure sensor. If the system pressure is too low, the hydraulic pump will be actuated. The hydraulic pump will build up pressure. When the system pressure has been reached, the SMG control unit will switch the hydraulic pump off again.



Gearshift
- The clutch disengages:
When a gearshift is initiated in manual or automatic mode the SMG control unit actuates the corresponding solenoid valves. The hydraulic fluid under pressure flows into the clutch slave cylinder. The clutch opens (disengages).
- The engine torque is reduced:
Simultaneously, the SMG control unit sends to the DME control unit the message that a gearshift is being initiated. The engine torque is reduced.
- Shifting:
The SMG control unit actuates the solenoid valves and the hydraulic shift cylinder. The shift cylinders execute the forwards and backwards movements of the corresponding shift rods. The desired gear is selected.
During the gearshift, the engine speed may be raised as required to allow the clutch engagement to be completed more quickly and more smoothly.
- Engagement:
When the gear is engaged, the clutch will automatically close.
After the gear change, the solenoid valves are actuated without the use of current.
The course of the entire gearshift depends on the accelerator pedal position, engine speed, road transmission speed and other controlled variables (e.g. engine oil temperature, selected driving program).
Gearshifts that would result in an excessively high or low engine speed are not executed.



Drivelogic
A total of 11 different driving programs are made available via "Drivelogic".
- In automatic mode there is a choice of 5 driving programs (from "relaxed" to "sporty").
In driving program 1, for instance, the 2nd gear is selected for pulling away. The clutch operates with great sensitivity. This eases pulling away on wintry roads.
- In manual mode there is a choice of 6 driving programs (from "adaptably dynamic" to "very sporty").
Driving program 6 is only available when DSC is deselected or with launch control.
The basic difference in the driving programs lies in their preselected shift times: The higher the driving program, the engine speed and the load, the shorter the shift time.



Driving in gear lever position "D" (automatic mode)
- Constant-speed travel
Continuous changes of the accelerator pedal position (opening and closing the throttle) are registered in the SMG control unit. The SMG control unit then suppresses a pendulum shift between adjacent gears (up and down, e.g. on a motorway journey with constantly changing speed).
- Upshift suppression
Based on the accelerator pedal position, the SMG control unit recognizes when the throttle is closed rapidly, e.g. before applying the brake.
The SMG control unit suppresses the upshift. This ensures that the engine braking effect is retained and supports the braking action.
- Manual intervention in automatic mode
If the gear lever or the gearshift paddles are operated in automatic mode, the system will automatically change to manual mode.
Automatic mode must be selected again.
- Driving uphill
The SMG control unit uses signals from the following components to recognize when the vehicle is driving uphill:
- Longitudinal acceleration sensor
- Wheel-speed sensors
- Accelerator pedal position
The SMG control unit prevents unintentional upshifts and irritating pendulum shifts.
- Driving downhill
The SMG control unit uses signals from the following components to recognize when the vehicle is driving downhill:
- Throttle valve potentiometer (load signal)
- Wheel-speed sensors (road speed)
- Brake light switch
The SMG control unit shifts down a gear as the road speed increases. This ensures that the engine braking effect is retained and increased.
- Braking deceleration and automatic downshift
The SMG control unit uses signals from the following components to recognize braking deceleration:
- Brake light switch
- Wheel-speed sensors
- Accelerator pedal position
The SMG control unit shifts down according to road speed to maintain the engine's braking effect. As this happens, several gears may be skipped. The correct gear is automatically selected when the vehicle accelerates again.



Launch control (acceleration assist system)
Launch control allows optimum vehicle acceleration from standstill, comparable to motor racing standards. For this to happen, the accelerator pedal only has to be quickly and fully depressed (kickdown).
When launch control is enabled, the system automatically shifts up through the gears, even in manual mode, for as long as the accelerator pedal is fully pressed down. This prevents the engine from reaching critical speeds.

Preconditions for enabling launch control:
- Vehicle standstill
- Dynamic Stability Control (DSC) deselected
- Driving program 6 selected at the for "Drivelogic" program switch
- Program "P 500" for engine control selected with the POWER button
- Sequential (manual) mode selected
- High-grip road surface

Important: Launch control can lead to increased wear of components.
Do not accelerate using launch control during the running-in phase of a new car. Frequent use of launch control leads to increased component wear.



Slip detection
A disproportionate amount of wheel slip may occur when engaging the clutch or during a load change (e.g. on wet or icy road surfaces). The clutch is disengaged to stabilize the vehicle.
The procedure is executed as follows:
- The clutch is opened after wheel slip is detected between the wheels on the rear axle and front axle on the same side. This counteracts the vehicle swerving out.
- Afterwards, the clutch engages softly in response to further wheel slip.
- The clutch opens and closes as required until no more wheel slip is detected when the clutch is closed.



Pulling away on a slope
Special software is loaded into the sequential M transmission to ease pulling away on a slope (on an uphill slope, the vehicle could roll back when the brakes are released).
The brakes intervene automatically to ease pulling away on a slope. The function may be used in both manual and automatic modes (when driving forwards and reversing).

This is initiated merely by pressing down the brake pedal when the vehicle is stationary. After the brake has been released, it is possible to drive off after approximately 0.8 seconds without rolling away out of control. During this time period, after the brake has been released the engine speed is increased to a level to match the slope. The clutch is moved to the clutch slipping point, which briefly prevents the vehicle from rolling back.



Vehicle standstill
The SMG control unit detects vehicle standstill from the accelerator pedal position, the wheel speeds and the engine speed. The clutch disengages. The 1st gear is selected (in manual and automatic modes).
If the driver's door or bonnet are opened when the engine is running, an acoustic signal draws attention to the position of the transmission. Reason: A drive position is still engaged and the transmission is not in position "N"). At the same time, the "N" symbol flashes in the LCD display in the instrument cluster.
If despite this, neither the pedals, the gearshift paddles nor the gear lever are moved, the gear will automatically be cancelled after approx. 2 seconds.



Gear lever position "Neutral" and ignition OFF
When the gear lever is in "Neutral" position and the ignition is switched off, the "N" symbol flashes in the LCD display of the instrument cluster. In addition, the multi-audio system controller (M-ASK) will emit an acoustic warning. Reason: The vehicle may roll away.)



Gear lever lock (shift-lock)
The gear lever lock prevents an unintentional gearshift.
When the vehicle is stationary, it is only possible to select a drive position when the brake is still applied and approximately 1.5 seconds after the "Neutral" gear lever position has been selected (for safety reasons).
The gear lever is locked in the "Neutral" position by an electromagnet (electromagnet locks in a current-free state). The electromagnet is actuated by the SMG control unit. The gear lever lock is engaged when selector lever position "N" is detected and the ignition (terminal 15) is ON.



Rocking free, e.g. from snow
To rock the vehicle free, shift gear rapidly from 1st gear, via position "N" to position "R" and vice versa. Perform the gearshift within approximately 0.8 seconds, as otherwise the gear lever lock (shift-lock) will be activated.



Protection of valves
All valves in the transmission are activated periodically to protect the valves from becoming soiled. In this process, the valves are supplied with current so that they are moved and cleaned, but the shift cylinder is not moved.
Switch-on conditions:
- During wake-up of the SMG control unit
- Cyclically after expiry of a specified time



Self-diagnosis during a pressure loss
Defects (e.g. leakage) are detected because the hydraulic pump switches on more frequently than is normal. The SMG control unit limits the switch-on time.
If there is a fault, the Check-Control symbol in the LCD display of the instrument cluster lights up.
When the hydraulic pump is running, the pressure increase is monitored in response to the switch-on time. The gear is deselected if there is a defect in the hydraulic pump or a pressure value is undercut (e.g. sudden pressure loss). The hydraulic control unit is deselected.



Emergency program
In the emergency program, the vehicle remains operational, albeit with limitations.
Depending on the type of transmission fault, the vehicle may no longer be operational after a vehicle standstill.

Operation



Activate launch control
(Note preconditions for activating launch control!)
The gear lever must be pushed forwards and the accelerator pedal must be pressed fully down. The engine is regulated to the optimum starting speed.
When the gear lever is released, the vehicle is accelerated with an ideally regulated slip for as long as the accelerator pedal is still pressed down.
The sequential M transmission with "Drivelogic" automatically changes gear from 1st to 7th until the top speed has been reached. Gearshifts are made shortly before the maximum engine number for the gear concerned is reached.

Deactivate launch control
- By the position of the accelerator pedal (releasing the kickdown position)
or
- By a manual gearshift
or
- By activating DSC
After a launch control operation, the vehicle must be driven over a certain distance before the next launch control operation is enabled.
Notes for service staff
Service staff should note the following points:

- General information:
- Diagnosis: ---
- Encoding/programming: ---
Subject to change.