Abstract: A method and system for a torque converter clutch solenoid functional test which discriminates between electronic component failures from other subsystem failures, such as mechanical or hydraulic failures utilizing a plurality of counters for monitoring the state of the solenoid (34) and other subsystem components.

Abstract: An electrohydraulic control system for an automatic transmission includes planetary gearsets, clutch and brakes that control the condition of the gear components, hydraulically actuated solenoid control valves, electronic sensors connected to a microprocessor, a gear selector mechanism and an overdrive cancel switch. The extent to which a gear ratio change is completed, as represented by the ratio of the current operating gear ratio and the gear ratio associated with gear ratio at the completion of the gear shift, is used as a variable in algorithms executed by the microprocessor to schedule change in state of solenoid operated valve. The state determines the engaged and disengaged condition of friction elements that produce the gear shift.

Abstract: In an electronically controlled transmission adapted to control operation of a torque converter clutch in softlock and hardlock modes, a test to determine whether the clutch is operating with an acceptable slip magnitude in a control region or whether it is operating with a high level of slip or instability outside the control region. The test distinguishes periods of instability associated with deterioration of the clutch from transients associated with normal operating conditions and background noise. An instability counter, interval clock and warm-up cycle counter are used to determine an appropriate point for discounting prior events and reentering the control test. Continuous slip mode of operation of the clutch is disabled entirely after a predetermined number of verified unstable events have occurred.