Abstract: A system for discriminating operation state of a lockup clutch of a torque converter of a transmission of a vehicle, more particularly to a system for detection a lockup clutch failure. In the system, three discrimination areas are preestablished with respect to the throttle opening and vehicle speed and reference value are determined in response to a selected discrimination area. The converter slip ratio is compared with the data and when the ratio is out of a range determined by the data, the lockup clutch operation is discriminated to be not normal. At that time, however, when the area is in a weak-engaged region, the engaging force is forcibly increased and the discrimination is conducted once again, thereby making it possible to conduct failure detection in the slip-engaged region and enhancing detection accuracy.

Abstract: A system for detecting malfunction of a transmission of a vehicle, more particularly a system for detecting a failure of a shift lever position sensor for a vehicle automatic transmission is provided with two detection modes based on urban driving and open-road driving. The number of times that the vehicle speed goes up and down between prescribed upper and lower values separately defined for the two modes is counted, when the shift lever position signal is absent. Probable failure is judged when the number of times reaches eight in the first mode and sensor failure is confirmed when the number of times reaches three in the second mode. Shift lever position sensor failure can be reliably detected irrespective of whether the driving environment is urban or open-road.

Abstract: It is an object of the present invention to provide a method of controlling the automatic transmission of a vehicle, in which the vehicle can be smoothly started on a low frictional coefficient road by requiring the concurrent operation of the brake pedal and the acceleration pedal. An up-shift operation will occur when both the brake and acceleration pedals are operated when the vehicle speed is less than a predetermined value.

Abstract: The present invention is directed to a method and apparatus for controlling an automatic transmission. A selector selects a first speed change range or a second speed change range in which the first and second speed change ranges effect speed changes at different points as a function of vehicle operating conditions. A microprocessor having a memory stores predetermined speed change patterns for the first and second speed change ranges and sensors are coupled to the microprocessor for sensing at least two vehicle operating conditions. The microprocessor controls the operation of the transmission in accordance with the vehicle operating conditions and the state of the selector. A selectively operable inhibiting device inhibits the transmission from operating in the maximum speed stage when the transmission is operating in the second speed change range.