AUTOMATIC TRANSMISSION
Fault finding - Role of components
23A
23A - 12V3 MR-372-J84-23A000$225.mif
AJ0 BVA
Vdiag No.: 04, 05AUTOMATIC TRANSMISSION
Fault finding - Role of components
The automatic transmission computer performs the following functions:
–Transmission operating mode selection:
According to the vehicle speed and the driver's request expressed by the accelerator pedal position, the automatic
transmission determines the best moment for the gear change. The automatic transmission computer corrects any
driver errors and inhibits engagement of a gear that would cause the engine to over- or under-rev.
–Gear changes:
Taking into account the various input factors, the computer will decide whether to actuate the various solenoid valves
to ensure smooth system operation (automatic transmission clutches, brakes and hydraulics).
The computer is also involved in:
–the gear change quality,
–protecting the automatic transmission in the event of a malfunction.
–Disengaging clutch when stopped:
This function enables creep* to be inhibited temporarily when the vehicle is stationary with a gear engaged and the
brake pedal depressed.
The aim of this function is to reduce drag on the vehicle in order to:
●reduce fuel consumption,
●reduce vehicle vibrations,
Creep*: describes the action of the vehicle moving forwards without acceleration and with a gear engaged.
MR-372-J84-23A000$225.mif
AUTOMATIC TRANSMISSION
Fault finding - Replacement of components
23A
23A-24V3 MR-372-J84-23A000$270.mif
AJ0 BVA
Vdiag No.: 04, 05
Replacing the transmission computer:
Remove the automatic transmission computer (see MR 370 mechanical, 23A, Automatic transmission,
Automatic transmission computer, Removal - Refitting).
Refit the automatic transmission computer (see MR 370 mechanical, 23A, Automatic transmission,
Automatic transmission computer, Removal - Refitting).
Establish dialogue with the diagnostic tool.
Use command VP001 Enter VIN.
Run command VP009 Write last After-Sales Service operation date.
Do not carry out any automatic programming if replacing the automatic transmission computer. Automatic
programming is finalised when the vehicle is driven.
In order to optimise the automatic programming before delivering the vehicle to the customer, apply the
"Programming procedure" shown below.
Replacing the hydraulic distributor:
Remove the transmission hydraulic distributor (see MR 370 mechanical, 23A, Automatic transmission,
Hydraulic distributor, Removal - Refitting).
Refit the transmission hydraulic distributor (see MR 370 Mechanical, 23A, Automatic transmission, Hydraulic
distributor, Removal - Refitting).
Replacing the automatic transmission
Remove the transmission (see MR 370,Mechanical, 23A, Automatic transmission, Removal - Refitting).
Refit the transmission (see MR 370, Mechanical, 23A, Automatic transmission, Removal - Refitting).
Establish communication with the diagnostic tool.
Initialise all the programming, use the command RZ009 Self-adapting clearing (Vdiag05 only).
Run command VP009 Write last After-Sales Service operation date.
The self-programming functions are performed when the vehicle is being driven.
In order to optimise the automatic programming before delivering the vehicle to the customer, apply the
"Programming procedure" shown below.
* APV: After-SalesPROGRAMMING PROCEDURE:
Programming conditions:
The automatic gearbox oil temperature should be between 60˚C and 100˚C.
Stationary, engine running, brake pedal depressed:
Engage neutral at least 5 times to consolidate the programming.
While driving:
Engage the same gear at least 5 times (i.e. in the same conditions) to consolidate the programming.
Note:
Gear changes are slow and harsh the first few times the vehicle is driven, until the automatic transmission computer
has carried out its automatic programming.
During upshifts and downshifts, the system analyses variations in oil pressure, components (play in the brakes and
clutches, changes to spring stiffness due to ageing) and input torque, then corrects them in order to maintain the
quality of gear changes.
The system analyses the turbine speed during the 3 phases of drag reduction (selection of Neutral when stationary,
regulation during drag reduction and deselection of Neutral) and corrects this speed by adjusting the converter
lock-up solenoid valve pressure.
