21B-8
MR-413-X44-21B000$177.mif
V2
21B
SEQUENTIAL GEARBOX
Fault finding - System operation
1. Sequential gearbox functions
The electrohydraulic system attached to the gearbox comprises two actuators, one for gear selection and changing,
the other for operating the clutch, and a hydraulic power unit which supplies power to the actuators.
The assembly is linked to the sequential gearbox computer, which itself is linked to the engine management
computer by a multiplex line connection. The gear lever is used to select gears: in automatic mode, gear changes
are controlled by the computer which uses auto-adaptive shift patterns; in manual mode, the driver moves a lever
which, via the computer, change the gears.
When the gear is changed, the sequential gearbox computer controls the engine management computer and the
torque in such a way as to reduce bucking, leaving the driver free to leave his foot on the accelerator pedal.
Description of user operation:
The interface between the driver and the sequential gearbox system inside the passenger compartment comprises:
–a gear lever (mechanical section and internal electronic section),
–a display,
–a buzzer.
Using this interface, the driver can:
–request gear changes (up or down),
–request a specific gear change (into neutral or reverse),
–switch between manual and automatic mode,
Description of passenger compartment control:
Description of gear lever positions:
–“S”: Standby: this is the only stable gear lever position. Each time the driver presses the lever, it returns to the S
position.
–“R”: Reverse: moving the lever to this position enables the driver to select reverse gear. Given the lever position
of the reverse function, if the movement is too slow, the sequential gearbox computer can read the N signal and
hence neutral is selected before reverse.
–“N”: Neutral: moving the lever to this position enables the driver to select neutral.
–“A/M”: AUTO/MANUAL: moving the lever to this position enables the driver to select either the manual mode (or
semi-automatic) or automatic mode. If AUTO mode is selected, moving the lever will enable the driver to select
manual mode, if manual mode is selected; moving the lever will enable the driver to select automatic mode. The automatic mode used by the sequential gearbox is based on the design of the DP0 automatic gearbox which
uses
shift patterns that adapt automatically to the driving style and road conditions.
The gear change is determined by a set of gear change graphs as a function of the accelerator pedal position and
the vehicle speed.
The sequential gearbox is a conventional manual gearbox with an electrohydraulic control.
Vdiag No: 04
MR-413-X44-21B000$177.mif
