Abstract: A control system for a vehicle includes an engine switch control unit for switching the operating condition of the engine between the all-cylinder operating condition and the partial-cylinder operating condition, a failure determining unit for determining the failure of the lockup clutch control device, and a coupling capacity change inhibiting unit for inhibiting a change in coupling capacity of the lockup clutch accompanied by the switch control of the operating condition of the engine by the engine switch control unit during the failure determination by the failure determining unit.

Abstract: In a system for controlling an internal combustion engine having a plurality of cylinders and connected to the automatic transmission and mounted on a vehicle and the operation of the engine is switched between full-cylinder operation during which all of the cylinders are operative and cutoff-cylinder operation during which some of the cylinders are non-operative, based on at least the load of the engine, a gradient of road on which the vehicle runs is estimated and the cutoff-cylinder operation is prohibited when the estimated gradient is equal to or greater than a threshold value. With this, it becomes possible to generate sufficient deceleration, when the vehicle runs a downhill during cutoff-cylinder operation, while ensuring to prevent the operator to feel excessive acceleration.

Abstract: A control system for a vehicle having an engine with a plurality of cylinders whose operating condition is switchable between an all-cylinder operating condition where all of the cylinders are operated and a partial-cylinder operating condition where a part of the cylinders is operated according to an operating condition of the vehicle, a torque converter with a lockup clutch connected to the engine, and a lockup clutch control device for controlling the lockup clutch.

Abstract: In a system for controlling an internal combustion engine having a plurality of cylinders and connected to the automatic transmission and mounted on a vehicle and the operation of the engine is switched between full-cylinder operation during which all of the cylinders are operative and cutoff-cylinder operation during which some of the cylinders are non-operative, based on at least the load of the engine, a gradient of road on which the vehicle runs is estimated and the cutoff-cylinder operation is prohibited when the estimated gradient is equal to or greater than a threshold value. With this, it becomes possible to generate sufficient deceleration, when the vehicle runs a downhill during cutoff-cylinder operation, while ensuring to prevent the operator to feel excessive acceleration.

Abstract: At downshifting, hydraulic pressure of hydraulic clutch on engaging side (ON clutch pressure) is increased when an input and output speed ratio ("Gratio") has fallen below a predetermined value YGDNS. YGDNS is variably set depending on the vehicle speed and the engine temperature so that it becomes a lower value at a high vehicle speed than at a low vehicle speed, and a higher value at a low engine temperature than at a high temperature. When a downshifting command to a still lower speed stage is issued during downshifting control (when FTBD=1), a downshifting completion processing is performed in the course of the downshifting control (step in S111). Oil pressure in a hydraulic engaging element on the disengaging side QDNOFF and oil pressure in a hydraulic engaging element on the engaging side QDNON are switched to the oil pressures at the time of completion of downshifting, to thereby complete the first step downshifting control at an early time.

Abstract: A system for controlling an automatic vehicle transmission, including a gear system and hydraulic clutches which hold a member of the gear system stationary to produce gear reduction or reverse, having an oil line which connects the clutches to an oil pressure source, a pressure control valve having a solenoid provided in the oil line which generates a regulated oil pressure to be supplied to the clutches in response to a current supplied to the solenoid, a switch valve provided in the oil line which switches the oil pressure to be supplied to the one of the clutches between the regulated oil pressure and a line pressure. In the system, it is discriminated whether the pressure control valve does not supply the regulated oil pressure to the clutches and if so, a dither current is supplied to the solenoid such that the valve repeatedly performs a vibrational motion to remove any grit therefrom, thereby removing grit without causing gear-shift shock or clutch vibration.

Abstract: A system for controlling an automatic transmission mounted on a vehicle, including a gear system and hydraulic clutches which hold a member of the gear system stationary to produce gear reduction or reverse to transmit engine output, and a linear solenoid valve provided in the oil line which generates an oil pressure to be supplied to hydraulic clutches in response to a current supplied thereto. In the system, the current supply is initiated when the ignition switch is turned to the ON position where the engine is not started, producing a noise due to the solenoid valve operation. In order to avoid this, the current is limited to a predetermined value when the engine is not started and the vehicle is stopped. Moreover, since the predetermined value is slightly above the current at which the clutch pressure begins to rise, the automatic transmission can start its operation quickly when the engine is started.