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The learned values are reset. Resetting the learned
values can briefly impair shifting quality until the
TCM has learned and stored the new values.
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Automatic Transmission/Transaxle
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Transmission Description – System Operation and ComponentDescription
System Operation
E112576
The AW55 5-gear automatic transaxle is a fully
automatic, electronically controlled automatic
transaxle. The fifth gear is an overdrive which
saves fuel.
The maximum input torque is 330 Nm.
Gear changes are controlled by an
electro-hydraulic system.
The gear ratios are achieved by means of a
combined planetary gear set and a Simpson set.
Three multi-plate clutches, four multi-plate brakes
and one band brake as well as two one-way
clutches control the various ratios.
The clutches and brakes are hydraulically operated
by electrically actuated solenoid valves. The valves
are actuated by the TCM depending on the driving
conditions and the driver's requirements.
The TCC is activated in gears 3, 4 and 5. The TCC
is driven in interlock mode and in slip mode. Defined slip achieves a smooth and therefore
comfortable clutch engagement of the TCC.
Control of slip mode depends on the engine speed,
accelerator pedal position and vehicle speed
signals provided by the ECM (engine control
module). This controls the rate of slip by comparing
the engine speed and the turbine shaft speed.
The TSS sensor and the OSS sensor use the Hall
effect principle. The TCM can regulate the slip in
the torque converter by comparing the engine
speed with the transmission speed.
All parameters for actuating the clutches and the
TCC are determined by the TCM as a function of
the operating parameters. The automatic transaxle
features a self-learning strategy.
The fundamental parameters for gear shifting are
the accelerator pedal position and the vehicle
speed.
Gear selection can either be performed
automatically or in select-shift mode. The selected
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transmission range or gear (in select-shift mode)
is indicated to the driver in the instrument panel.
In selector lever position "S", the driver can
manually select the gears (select-shift mode). Up
(+) and down (-) shifts are made by moving the
selector lever in the appropriate direction.
Hydraulic limp home modes maintain limited
operation in the event of failure of important
electrical components.Under normal conditions, the transmission fluid is
filled for the service life of the transaxle and does
not need to be changed.
A dipstick is used to check the fluid level in the
transmission.
Functionality overview
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E125524
Description
Item
Electronic Control System
A
Hydraulic Control System
BDescription
Item
Select-shift switch module
1
CAN (controller area network) bus input
signals
2
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Description
Item
The TR sensor
3
The TSS sensor
4
The TFT sensor
5
TCM6Description
Item
OSS (output shaft speed) sensor
7
Solenoid valves in valve body
8
Clutches and brakes
9
TCC
10
The function is divided into an electronic and a
hydraulic control system.
Electronic Control System
Depending on the input signals, the TCM mounted
on the transmission actuates the solenoid valves
in the valve body. The TCM calculates and stores
adaptive data, fault codes and values for diagnosis.
The TR sensor is integrated in the TCM.
Hydraulic Control System
When the engine is running, a fluid pump integrated
in the transaxle housing generates the hydraulic pressure required for controlling the automatic
transaxle.
Through actuation of the solenoid valves, hydraulic
pressure is applied to the clutches and brakes via
hydraulic channels in the valve body and the
transaxle. The control valves regulate the hydraulic
pressure in accordance with the duty cycle of the
electrical PWM signal. The controlled hydraulic
pressure enables smooth shifting or the generation
of a defined slip through actuation of the relevant
clutches and brakes.
Solenoid valves are either in the 'open' or 'closed'
state.Type plate
E125523
The transaxle identification is located on the
rear/top of the transaxle housing in the direction of
travel.
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Serial number of the transmission
Example:09HV70001
• 09: year of manufacture, 2009 •
H: code letter for the month of manufacture,
August
• V7: automatic transaxle type 55-51SN
• 00001 : Production number for the specified
month
Identification letter coding
January
A
February
B
March
C
April
D
May
E
June
F
July
G
August
H.
September
J
October
K
November
left-hand
December
Ground
Markings on the TCM
E125774
The name plate is located on the TCM.
Serial number of the TCM
Example: 082200001
• 08: year of manufacture, 2008
• 22: code for the calendar week
• 00001 : Production number for the specified
calendar week
Transmission Control
Depending on the input signals, the TCM mounted
on the transmission actuates the solenoid valves
in the valve body. The TCM calculates and stores
adaptive data, fault codes and values for diagnosis.
The TR sensor is integrated in the TCM.
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E112322
The TCM adapts the gear changing to ensure that
the correct gear is selected for the style of driving,
the engine load, driver requirements, vehicle speed
etc. This leads to lower fuel consumption together
with improved comfort through smoother gear
changes and lower noise levels.
The TCM receives information on the driver's
desired transmission range and type of driving
mode. In contrast to a transmission which is only
controlled hydraulically, the control module can
calculate the best times to shift gear and activate
torque converter lockup by using the signals from
the sensors in the transmission and the engine
management system.
The control module enables small changes in the
operating conditions to be made and adapts thevarious transmission functions to ensure that the
correct gear is always selected in relation to the
type of driving mode.
The TCM has adaptive capabilities. This ensures
smooth gear changes throughout the whole service
life of the transmission.
To exactly determine the activation points of the
gear shifts and torque converter lockup on the
basis of the type of driving mode chosen, the TCM
receives the following information:
• Transmission range chosen (TR sensor).
• Type of driving mode chosen
(normal/sport/select-shift).
• Transmission input shaft speed (TSS sensor).
• Transmission output shaft speed (OSS sensor).
• Transmission fluid temperature (TFT sensor).
• The engine speed and the torque as well as the throttle plate opening - from the PCM via the
CAN data bus.
• Actuation of the accelerator pedal - from the PCM via the CAN data bus.
• Coolant temperature - from the PCM via the CAN data bus.
• Vehicle speed - from the ABS via the CAN data bus.
• Actuation of the brake pedal - from the ABS via the CAN data bus.
Pin assignment for TCM connector 'A' (connection to vehicle)
11
E125669
Description
Item
Battery (+)
1
not assigned
2Description
Item
not assigned
3
not assigned
4
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Description
Item
Starter motor inhibitor signal to the PCM
5
CAN (low)
6
LIN (local interconnect network)
7
CAN (high)
8
GND (ground)
9
not assigned
10Description
Item
Battery (+) via ignition switch
11
not assigned
12
Selector lever lock
13
not assigned
14
not assigned
15
Voltage supply for select-shift switch
module
16
Pin assignment for TCM connector 'B' (connection to transaxle)
E125670
Description
Item
OSS(–)
1
OSS(+)
2Description
Item
TSS(+)
3
TSS(–)
4
Pin assignment for TCM connector 'C'
(connection to transaxle)
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