2007 FORD FIESTA transmission

Automatic Transmission/Transaxle -
Vehicles With: 4-Speed Automatic
Transmission
(AW81-40)
DESCRIPTION AND OPERATION
Transaxle Electronic Control System
Overview
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2006.0 Fiesta 1212006 G380530en
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Automatic Transmission/Transaxle -
Vehicles With: 4-Speed Automatic
Transmission (AW81-40)
DESCRIPTION AND OPERATION
Item Description
1 5 1 Generic Electronic Module (GEM) I
I
1 6 1 Turbine Shaft Speed (TSS) sensor I
1 7 1 Output Shaft Speed (OSS) sensor I
1
2
3
4
l tem Description
Transmission control unit
Data Link Connector (DLC)
Powertrain Control Module (PCM)
Instrument cluster
1 8 I Transmission Range (TR) sensor I
1 9 1 Starter inhibit relay I
1 10 1 Backup lamp relay I
11 Transmission Fluid Temperature (TFT)
I I sensor
1 12 loverdrive switch I
1 13 1 Driver's side door ajar switch I
1 14 1 Solenoid valves in the main control body 1
Transmission control unit
Item Description
Electrical connector, vehicle wiring
harness
connector, transmission wiring
harness
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The transmission control unit is located in the
'engine compartment on the left-hand side member.
The transmission control unit evaluates incoming
signals and controls the actuators accordingly.
2006.0 Fiesta 1212006 G380530en
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Automatic Transmission/Transaxle -
Vehicles With: 4-Speed Automatic
307-01 -30 Transmission (AW81-40) 307-01 -30
DESCRIPTION AND OPERATION
The transmission control unit can be diagnosed
with WDS via the DLC.
Gearshift strategies
Gearshift control
I A I Accelerator pedal position I
I B I vehicle speed 1
The current ratio is selected by the transmission
control unit either in accordance with the
requirements for low fuel consumption or in order
to meet the required driving performance.
The gearshift timing is selected in accordance with
a gearshift map which is programmed into the
control unit as a function of the accelerator pedal
position and the vehicle speed.
For kick-down (accelerator pedal pressed down at
least
95 %) the next lowest gear is selected, as
long as the engine speed allows it. All gearshift
timings are set by the transmission control unit to
the upper shift characteristic. The driver can feel the
kickdown point
in the
accelerator pedal as a slight increase in resistance
to the operation of the pedal.
This is influenced by the following variables:
accelerator pedal position and actuation,
vehicle speed,
brake pedal position,
selector lever position.
The following are actuated:
SSA shift solenoid valve,
SSB shift solenoid valve.
Hill climb mode
When the vehicle is in hill climb mode or towing a
trailer, the transmission control delays gearshifts
to prevent frequent shifting back and forth between
the gears.
2006.0 Fiesta 1u2oos
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Automatic TransmissionlTransaxle -
Vehicles With: 4-Speed Automatic
307-01 -31 Transmission (AW81-40) 307-01 -31
DESCRIPTION AND OPERATION
The transmission control unit determines hill climb
mode or trailer operation from the change in throttle
; valve position supplied by the PCM in relation to
the acceleration of the vehicle.
Depending on the driving resistance, the
transmission control unit chooses between two
gearshift maps which have been specially
programmed for this purpose and in which the shift
timings are again chosen as a function of the
accelerator pedal position and the vehicle speed..
Hill descent mode
The hill descent mode is used to take better
advantage of engine braking during hill descents.
A 'hill descent' situation is recognised by the
transmission control unit if the vehicle is
accelerating without operation of the accelerator
pedal.
If in addition the brake is also depressed then the
transmission control unit automatically shifts back
from 4th into 3rd gear.
( ' Cold start mode
In order to reach operating temperature as quickly
as possible under low ambient temperatures,
gearshifts into 4th gear and engagement of the
torque converter clutch (TCC) are suppressed if
one of the following conditions is met:
Transmission fluid temperature below +20 "C
Coolant temperature below - 40°C
The following are actuated: SSA shift solenoid valve,
SSB shift solenoid valve,
Shift solenoid valve, TCC.
Overheating protection mode
The overheating protection mode serves to protect
the transmission against overheating and the
serious damage that this can cause.
If the transmission fluid temperature reaches a
temperature of around 135
"C, the transmission
control employs a shift pattern designed to prevent
a further increase in the transmission fluid
temperature. When
the transmission fluid temperature drops
back below approx. 125
"C, the transmission
control exits the overheating protection mode.
The MIL warning lamp is actuated by the
transmission control unit if the transmission fluid
temperature reaches approximately 140
"C.
The MIL warning lamp goes out again when the
transmission fluid temperature drops back to below
around 130
"C.
Main line pressure control
In order to ensure the highest possible efficiency
of the automatic transmission and to limit the power
losses from the fluid pump, the main line pressure
is adapted accordingly by the main regulating valve
as a function of the accelerator pedal position
(driver torque demand) and the selector lever
position.
This is influenced by the following variables:
Accelerator pedal position and actuation
Selector lever position
The following are actuated:
Main 'regulating valve
Engagement of the TCC
The TCC is engaged in 3rd and 4th gear depending
on the current driving situation.
Engagement is controlled in accordance with the
shift map stored in the control unit.
This is influenced by the following variables:
Accelerator pedal position and actuation,
Vehicle speed,
Selector lever position,
Transmission fluid temperature,
Coolant temperature.
The following are actuated:
Shift solenoid valve, TCC.
Torque reduction during gearshifts
In order to improve the quality of gearshifts and to
avoid gearshift judder, the engine torque is reduced
by the PCM in response to a request from the
transmission control unit during gearshifts.
The engine torque is also reduced during
engagement and disengagement of the TCC.
2006.0 Fiesta 1212006 G380530en
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Automatic Transmission/Transaxle -
Vehicles With: 4-Speed Automatic
307-01 -32 Transmission
(AW81-40) 307-01 -32
DESCRIPTION AND OPERATION
This is influenced by the following variables:
Engine speed,
Engine load,
Transmission input speed,
Vehicle speed.
The following are actuated:
PCM (torque reduction request signal via the
CAN databus).
Pressure control during gearshifts
In order to ensure that the engagement of the
clutches and brakes is as judder-free as possible,
the main line pressure is reduced during gearshifts.
This is influenced by the following variables:
Enginespeed,
Engine load,
Transmission input speed,
Vehicle speed.
The following are actuated:
Main regulating valve.
Shift timing adaptation during upshifts
In order to ensure that the engagement of the
clutches and brakes is as judder-free as possible,
the timing of the gearshift processes is monitored
during upshifts.
In the event of any discrepancy from the target
values, the main line pressure is adapted
accordingly during the next gearshift.
The shift timing adaptation during upshifts is only
active at transmission fluid temperatures between
50
"C and 120 "C.
This is influenced by the following variables:
Engine load,
Accelerator pedal position,
Transmission input speed,
Vehicle speed,
Transmission fluid temperature,
Selector lever position.
The following are actuated:
Main regulating valve.
Shift timing adaptation during shifts from
3rd to 4th gear
The shift from 3rd gear into 4th gear is the only
gearshift during which a clutch is disengaged and
a brake is engaged simultaneously.
In order to control the synchronized switching of
the two components as exactly as possible, the
shifl timing solenoid valve is actuated accordingly.
In order to ensure that this particular gearshift is
performed as judder-free as possible throughout
the service life of the transmission, the gearshift is
monitored by the two rotational speed sensors and
the actuation of the shift timing solenoid valve is
adapted accordingly.
The shift timing adaptation for gearshifts from 3rd
gear into 4th gear is only active at transmission
fluid temperatures between 30
"C and 120 "C.
This is influenced by the following variables:
Engine load,
Accelerator pedal position,
Transmission input speed,
Vehicle speed,
Transmission fluid temperature,
Selector lever position.
The following are actuated:
Shift timing solenoid valve.
Shift timing adaptation during shifts from
4th to 3rd gear
The shift from 4th gear into 3rd gear is the only
gearshift during which a brake is disengaged and
a clutch is engaged simultaneously.
In order to control the engagement of the clutch as
precisely as possible, the main regulating valve is
actuated accordingly in order to build up the
actuating pressure at exactly the right time.
In order to ensure that this particular gearshift is
performed as judder-free as possible throughout
the service life of the transmission, the gearshift is
monitored by the two rotational speed sensors and
the actuation of the main regulating valve is
adapted accordingly.
The shift timing adaptation for gearshifts from 4th
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gear into 3rd gear is only active at transmission (
fluid temperatures between 20 "C and 120 "C. .
2006.0 Fiesta 1212006 G380530en
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Automatic Transmission/Transaxle -
Vehicles With: 4Speed Automatic
307-01 -33 Transmission (AW81-40) 307-01 -33
DESCRIPTION AND OPERATION
This is influenced by the following variables: Vehicle
speed,
Engine load, Transmission fluid temperature.
Accelerator pedal position, The following are actuated:
Transmission input speed, SSA shift solenoid valve,
Vehicle speed,
Transmission fluid temperature,
Selector lever position.
The
following are actuated:
Main
regulating valve.
Reverse gear safety strategy
SSB shift solenoid valve.
Torque reduction when pulling away
In order to protect the clutches against excessively
high torque when pulling away, the PCM reduces
the engine torque in response to a request from
the transmission
control.
If the accelerator pedal is depressed while the
The transmission control unit prevents shifts into vehicle is pulling away, then the transmission reverse gear while the vehicle is driving forwards, control unit sends a corresponding signal as otherwise serious transmission damage can be requesting a torque reduction via the CAN databus. caused.
The reverse gear safety strategy is active when This
is influenced by the
following variables:
reverse gear is engaged with the selector lever at ' Selector lever position,
vehicle speeds in excess of 11 kmlh. Accelerator pedal position,
In this
case the transmission control unit actuates ' Engine speed,
the shift timing solenoid valve, as a result of which Transmission input speed,
the actuating pressure does not reach the reverse
. Vehicle speed. gear clutch or the reverse gear brake.
The following are actuated:
The reverse gear safety strategy is deactivated
PCM (torque reduction request signal via the
when the vehicle speed is below 9 kmlh. The
actuating pressure can then reach the reverse gear CAN
databus).
clutch and the reverse gear brake and the gearshift
into reverse gear is performed.
Selector lever positions
This is influenced by the following variables:
Vehicle speed,
Selector lever position.
The
following are actuated:
Shift timing solenoid valve.
Selector lever position "P"
No gear is engaged in selector lever position "P".
The parking
pawl is engaged manually via the
selector lever cable and the selector shaft.
Avoidance of gearshift judder during
engagement of a transmission range Selector
lever position "R"
In order to prevent gearshift judder when moving The reverse gear is eWaged in selector lever
the selector lever from N to D, the transmission position "R.
control unit initially shifts into
2nd gear instead of
1 st gear, and then immediately shifts back into I st
gear before the gearshift process is finished. Selector lever position "N"
This reduces the amount of gearshift judder during No gear is engaged in selector lever position WNW. engagement of a forward drive range.
The powertrain is not blocked. This is influenced by the following variables:
Selector lever position,
Accelerator pedal position,
Transmission input speed,
2006.0 Fiesta 1212006 G380530en
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Automatic Transmission/Transaxle -
Vehicles With: 4Speed Automatic
307-01 -34 Transmission (AW81-40) 307-01 -34
DESCRIPTION AND OPERATION
Selector lever position "D" In selector lever position "2" engine braking is
effective when the vehicle is coasting.
In selector lever position
"D" the transmission
control will allow all gears to be engaged provided
the overdrive switch is not operated.
Selector lever position "1"
If the overdrive switch is pressed then the
Only the first gear is engaged when the selector
transmission control prevents gearshifts into 4th
lever is in position ,,. gear or shifts back into 3rd gear.
Selector lever position "2"
If the selector lever is moved to position "1" at
higher speeds than are permitted for first gear, then
the transmission control delays the downshift until
the vehicle speed has slowed down enough.
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Only the second gear is engaged when the selector In selector lever position ,, engine braking is lever is in position "2". Gearshifts into 1st gear are effective when the vehicle is not permitted.
If the selector lever is moved to position
"2" at
higher speeds than are permitted for second gear,
then the transmission control delays the downshift until the vehicle speed has slowed down enough.
Signal transmission on the CAN databus
CAN Low
E48 1 88
Item Description Item Description
I 1 1 Transmission control unit 1 3 1 Instrument cluster
2006.0 Fiesta 1~2006 G380530en
2 PCM 4 DLC
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Automatic Transmission/Transaxle -
Vehicles With: 4Speed Automatic
307-01 -35 Transmission (AW81-40) 307-01 -35
DESCRIPTION AND OPERATION
Engine speed
1 The engine speed is detected by the crankshaft
position (CKP) sensor and passed on to the PCM.
The engine speed is transmitted from the PCM via
the CAN
databus to the transmission control unit.
The transmission control unit uses this signal for:
Torque reduction during gearshifts,
Pressure control during gearshifts.
Engine load
The PCM determines a load signal which is
transmitted via the CAN
databus to the
transmission control unit.
The transmission control unit uses this signal for:
Torque reduction during gearshifts,
Pressure control during gearshifts,
Shift timing adaptation during upshifts,
Shift timing adaptation during shifts from 3rd to
4th gear,
Hill climb mode,
( ' Hill descent mode. ' ,
Torque reduction request signal
Before performing a gearshift, the transmission
control unit sends a signal via the CAN
databus to
the PCM requesting a torque reduction.
The PCM then reduces the engine torque, ensuring
that the gearshift is as smooth and judder-free as
possible.
Brake signal
The PCM receives a signal from the stoplamp
switch when the brake pedal is depressed.
This signal is transmitted via the CAN
databus to
the transmission control unit.
The transmission control unit uses this signal for:
Gearshift control,
Engagement of the TCC
Accelerator pedal position
The PCM receives the current accelerator pedal
position signal from the Accelerator Pedal Position
(APP) sensor.
This signal is transmitted via the CAN
databus to
the transmission control unit.
The transmission control unit uses this signal for:
Controlling the main line pressure,
Gearshift control,
Engagement of the TCC,
Shift timing adaptation during upshifts,
Shift timing adaptation during shifts from 3rd to
4th gear,
Shift timing adaptation during shifts from 4th to
3rd gear,
Avoidance of gearshift judder during
engagement of a transmission range,
Torque reduction when pulling away.
Coolant temperature
The coolant temperature is detected by the Engine
Coolant Temperature (ECT) sensor and passed
on to the PCM.
This signal is transmitted via the CAN
databus to
the transmission control unit.
The transmission control unit uses this signal for:
Cold start mode,
Engagement of the TCC
Selector lever position
The transmission control unit transmits the selector
lever position to the instrument cluster.
The instrument cluster uses the signal to send a
request for a warning tone to the GEM when the
selector lever is not in position "P" and the driver's
door is opened.
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2006.0 Fiesta 1212006 G380530en
procarmanuals.com