Abstract: A control system and method for an automated mechanical transmission system (10) including an engine braking mechanism (14A) is provided for allowing operator request for an automatic direct downshift into the selected ratio (GR.sub.EB) automatically determined to provide optimum engine braking under current vehicle operating conditions. Retaining the control lever (1) in a displaced position for longer than a reference period of time (REF), such as one or two seconds, while the engine brake is active, will initiate the automatic determination and shift into the selected ratio (GR.sub.EB) determined to provide optimum engine braking under current vehicle operating conditions procedure.

Abstract: Open-circuit and closed-circuit faults in a solenoid controlled actuator are detected using shunt resistors (R1, R4) across the solenoid (1), a transistor switch (4), and a voltage monitor (7) and/or (14) across one or both of these which can detect a faulty open-circuit solenoid that is not energized, or a faulty closed-circuit solenoid that is energized. According to the present invention, before each change in actuator position, the solenoids are all caused to assume an opposite energization condition for a period of time insufficient to move the actuator, but enough to check the voltage monitor responses. In this way, both open and closed circuit faults are detected.

Abstract: An emergency device (2) for allowing manual limp home/get off road shifting of an automatic/semiautomatic mechnical transmisssion of the type having an electrically controlled shifter (30) including a plurality of electrically initialed shifting drivers (solenoids S1-S6) is provided.