3315764 - E7050 AUTOMATIC TRANSMISSION - Functional description (Automatic transmission)
Functional description
The electronic automatic transmission (EAT) control unit M55 monitors and governs the entire automatic transmission management system. The control unit is supplied directly by the battery via the line of maxifuse CENTR of B5 , to pin 55 of M55 via a line protected by fuse F10 of junction unit B1 . Ignition-operated power supply (INT/A) reaches pin 31 and 54 of M55 via a line protected by specific fuse B42 . Pins 6, 28 and 34 of control unit M55 are earthed.Control unit M55 is connected to EAT solenoid L50, which contains the valves which control the pressure regulators and certain sensors:
- pin 52 of M55 supplies the solenoids, whose control signals are sent from pins 30 and 33 of M55 ;
- pin 3 of M55 supplies the pressure regulators, whose control signals are sent from pins 1, 4, 5 and 29 of M55 ;
- pins 14, 15 and 42 of M55 are connected to the car speed sensor inside unit L50 ;
- pins 16, 23 and 44 of M55 are connected to the transmission input rpm sensor inside unit L50 ;
Control unit M55 is connected to the EAT sensor unit via junction D79:
- pin E of D79 is supplied directly from the battery via the line of maxifuse CENTR of B5 , via a line protected by fuse F10 of junction unit B1 : pin K is earthed.
- pins G and H of D79 are connected to the reversing sensor and send signals to turn on the reversing light ( See E2022 REVERSING LIGHTS)
- Pins A, B, C and D of D79 are connected to control unit M55 and indicate the positions assumed by the lever selector to pins, 36, 8, 37 and 9 of M55 respectively.
Control unit M55 governs a series of safety checks:
- shift lock (lever locked if key not turned to MAR and brake pressed): sends a signal from pin 32 to the speed control unit H37 pin 14;
- key lock (key locked if the gear shift is not set to P): sends a signal from pin 48 to relay J6 : this is excited by electrical current from the battery via line of maxifuse CENTR of B5 via a line protected by fuse F17 of junction unit B1 and controls the lock electromagnet built into ignition switch H1 ;
- doors open buzzer: the signal that the driver's door is open - lock N50 reaches pin 45 of M55 ; the command for the buzzer, located in C pin 11, is sent from pin 51
- start-up (the engine will start only with the gear shift set to P or N): a signal is sent from one of the two sensors (pin I of connector D79 to relay J5 which enables start-up: pin 50 of starter motor A20 ( See E5010 STARTING AND RECHARING).