Page 9 of 162

AUTOMATIC TRANSMISSION
Fault finding - Role of components
23A
23A - 9V3 MR-372-J84-23A000$135.mif
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Vdiag No.: 04, 05AUTOMATIC TRANSMISSION
Fault finding - Role of components
Role of main automatic transmission components
Automatic transmission computer:
The gearbox computer is used to manage the entire system.
Its role is to define the optimum operating mode for the automatic transmission (modify the torque transmitted to the
drive wheels by the automatic transmission), inform the driver (instrument panel, information display, buzzer) and
communicate with the other computers.
To carry out this function, the transmission computer takes account of:
–the operation of the gearbox,
–signals exchanged with other computers,
–driver requests.
Transmission oil temperature sensor:
Its role is to inform the automatic transmission computer of the transmission oil temperature.
Transmission input speed sensor:
Its role is to inform the automatic transmission computer of the turbine speed.
Transmission output speed sensor:
Its role is to inform the automatic transmission computer of the vehicle speed.
Brake light switch:
Its role is to inform the automatic transmission computer that the driver has depressed the brake pedal.
Multifunction switch:
Its role is to inform the automatic transmission computer of the gear lever position.
Shift-lock:
The role of this function is to lock the lever in position "P" and to immobilise the vehicle when stationary.
Solenoid valves:
The solenoid valves are fitted in the factory and cannot be removed from the hydraulic distributor to ensure optimum
gearbox operation, therefore they cannot be replaced separately.
The automatic transmission has two types of solenoid valve:
–2 "all or nothing" solenoid valves,
–6 "progressive" solenoid valves.
Of these 8 solenoid valves, 7 are used to control gear changes in automatic and manual modes, and one solenoid
valve controls the oil pressure in the automatic transmission hydraulic distributor.
Instrument panel display:
The purpose of this function is to manage the transmission of multiplex line signals required for the instrument panel
display.
On the instrument panel:
–a fault warning light,
–a message on the instrument panel in case of irregularity,
–an information display: gear lever position/gear engaged/brake pedal depressed indicator light/lever position in P
or N request indicator light.
On the gear lever:
–Position: P / R / N / D / M+/-,
–Shift-lock: lever lock.
MR-372-J84-23A000$135.mif
Page 10 of 162
AUTOMATIC TRANSMISSION
Fault finding - Operating diagram
23A
23A - 10V3 MR-372-J84-23A000$180.mif
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Vdiag No.: 04, 05AUTOMATIC TRANSMISSION
Fault finding - Operating diagram
Line pressure
OIL PUMP
Hydraulic
distributor
Primary regulation valve (pressure regulating valve)
LS pressure regulation solenoid valve
Manual valve
Clutch
modulating
solenoid valve 1
Clutch
modulating
solenoid valve 2Clutch
modulating
solenoid valve 3Brake
modulating
solenoid valve 2Modulating solenoid
valve
lock-up/brake 1
Sequence
solenoid valve 1Sequence solenoid
valve 2
Clutch 1 Clutch 2 Clutch 3 Brake 2Brake
1Torque
converter
lock-up
Hydraulic receivers
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Page 11 of 162
AUTOMATIC TRANSMISSION
Fault finding - Operating diagram
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23A - 11V3 MR-372-J84-23A000$180.mif
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Vdiag No.: 04, 05
Hydraulic distributor
Clutch modulating
solenoid
valve 1Clutch modulating
solenoid
valve 2Clutch modulating
solenoid
valve 3Brake modulating
solenoid
valve 2Modulating solenoid
valve, lock-up/brake 1
Sequence
solenoid valve 1Sequence solenoid valve 2
Clutch 1
pressure switchClutch 2
pressure switchClutch 3
pressure switchBrake pressure
switch 2Brake pressure
switch 1
Clutch 1 Clutch 2 Clutch 3 Brake 2 Brake 1Torque
converter
lock-up
Hydraulic receivers
Line pressure
Page 14 of 162
AUTOMATIC TRANSMISSION
Fault finding - Role of components
23A
23A - 14V3 MR-372-J84-23A000$225.mif
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Vdiag No.: 04, 05
"GEAR CHANGE" FUNCTION:
Purpose of this function:
The purpose of this function is to control gear changes in automatic and manual modes.
"Lever selection"
function
"Gear
change"
functionClutch 1
solenoid valve
Brake pedal action Brake 2 solenoid valve
Vehicle speed Clutch 2 solenoid valve
Turbine speed Clutch 3 solenoid valve
Lock-up and brake 1
solenoid valve
Solenoid valve EVS1
Solenoid valve EVS2
–Accelerator
–Engine speed
–Gear change inhibition
–...CAN
"Torque management"
function
Page 16 of 162
AUTOMATIC TRANSMISSION
Fault finding - Role of components
23A
23A - 16V3 MR-372-J84-23A000$225.mif
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Vdiag No.: 04, 05
"PRESSURE CONTROL" FUNCTION:
Purpose of this function:
The purpose of this function is to regulate the oil pressure inside the transmission hydraulic distributor.
"Lever selection"
function
"Pressure
control"
function Oil temperature
Line pressure solenoid
valve
Vehicle speed
Turbine speed
–Accelerator pedal
position
–Engine speed
–Engine torqueCAN
"Gear change" function
Page 17 of 162
AUTOMATIC TRANSMISSION
Fault finding - Role of components
23A
23A - 17V3 MR-372-J84-23A000$225.mif
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Vdiag No.: 04, 05
"CONVERTER lock-up" FUNCTION:
Aim of this function: The aim of this function is to lock up the converter.
–lock-up/release definition:
The converter is a hydraulic clutch which provides a hydraulic connection between the engine and the automatic
transmission pressure plate.
The purpose of the lock-up function is to lock the turbine and the converter casing together, transforming a hydraulic
connection into a mechanical connection. The role of the lock-up function is to prevent slipping losses.
EVS2*: sequence solenoid valve 2."Lever selection"
function
"Converter
lock-up"
functionLock-up and brake 1
solenoid valve
Solenoid valve EVS2*
Oil temperature
Vehicle speed
Turbine speed
Brake pedal action
"Torque management"
function
–Accelerator pedal
position
–Engine speed
–Engine torqueCAN
"Gear change" function
Page 18 of 162
AUTOMATIC TRANSMISSION
Fault finding - Role of components
23A
23A - 18V3 MR-372-J84-23A000$225.mif
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Vdiag No.: 04, 05
"TORQUE MANAGEMENT" FUNCTION:
Purpose of this function:
The purpose of this function is to manage the torque setpoints during certain gear shifts by informing the injection
computer. This function means smoother gear shifts and better mechanical protection.
–Accelerator pedal
position
–Engine speed
–Engine torqueCAN
"Torque
management"
function Vehicle speed
CAN–Torque request
–Torque converter status
–Gear changes
(in progress)
Turbine speed
"Gear change" function
Page 21 of 162

AUTOMATIC TRANSMISSION
Fault finding - Replacement of components
23A
23A-21V3 MR-372-J84-23A000$270.mif
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Vdiag No.: 04, 05AUTOMATIC TRANSMISSION
Fault finding - Replacement of components
*sig.: signal
*EVS1 = shift solenoid valve 1
*EVS2 = shift solenoid valve 2
*LS = line pressure regulation solenoid valveTool fault Diagnostic tool title Defect modes
DF023Transmission oil temperature sensor
circuit–in the event of open circuit or short circuit+:
If the fault occurs while driving, the
transmission engages fixed 5
th gear.
Restarting is in 3rd gear.
–in the event of short circuit-:
No defect mode.
DF038Turbine speed sensor circuit If the fault occurs while driving:
Gear fixed. Restarting is in fixed 3
rd gear.
DF067Lever switch circuit No defect mode.
DF084Multiplex network If the fault occurs while driving, the
transmission engages fixed 5
th gear.
Restarting is in 3rd gear.
DF085EVS1 shift solenoid valve circuit – in the event of open circuit or short circuit+:
Fixed 5
th gear engaged.
Restarting is in 5th gear.
–in the event of short circuit-:
No defect mode.
DF086ESV2* shift solenoid valve circuit Fixed 5
th gear engaged.
Restarting is in 3rd gear.
DF091"LS"* pressure regulation solenoid
valve circuitNo defect mode.
DF093Manual sequential controls circuit No defect mode.
DF095Gear lever lock electromagnet circuit No defect mode.
DF097Converter lockup No defect mode.
DF108Effective average torque multiplex
signalIf the fault occurs while driving, the gearbox
engages fixed 5
th gear. Restarting is in 3rd
gear.
DF171Vehicle speed sensor circuit If the fault occurs while driving:
Gear fixed. Restarting is in fixed 3
rd gear.
DF178Accelerator pedal position No defect mode.
DF183No UCH multiplex signal. No defect mode.
DF186No injection multiplex signal If the fault occurs while driving, the gearbox
engages fixed 5
th gear.
Restarting is in 3rd gear.
DF230Signal: multiplex speed vehicle invalid No defect mode.
MR-372-J84-23A000$270.mif