Abstract: In a vehicular automatic transmission of an engaging pressure electronically controlled type, a failures detecting apparatus is installed to detect an occurrence of failure of a hydraulic switching device such as a hydraulic switching valve and includes: a gear range determinator to determine in which gear range the present gear range of the automatic transmission falls; a failure detection start determinator to determine a start of the failure detection of the hydraulic switching device according to a result of determination by the gear range determinator; a memory storing parts of a plurality of engaging elements which are selected as the combinations of engagement for the respective gear ranges and other parts than those for the respective gear ranges in a table form; a hydraulic switching device checking device to intentionally output an engagement command signal to command to engage to each of the other parts of engaging elements which are not to be engaged and which are read from the memory; and a hydra

Abstract: The analog output of a throttle valve position sensor is A/D converted in an engine control unit and the digital signal is subject to a correction which corrects the position indicated by the signal to one which accurately reflects the position of the throttle valve. The corrected valve is then converted into a PWM signal and transmitted to a transmission control unit. The PWM signal is de-coded and used for transmission control purposes. If the position sensor malfunctions, the characteristics of the PWM signal under such circumstances reflects the improper operation thus enabling the transmission control circuit to issue a signal indicative of the situation. Only one line is required to transmit the data between the engine and transmission control units.

Abstract: In order to obviate rapid on/off hunting of an engine idle detection circuit which is operatively connected with a throttle valve position sensor, the detection circuit outputs an idle indication when the throttle valve opening is indicated as having fallen below a first predetermined level which is proximate the fully closed one. The idle indication is maintained until such time as the throttle valve is indicated as having opened beyond a second predetermined level which is slightly greater than the first one.