The Automatic Transmission changes the gear position of the transmission utilizing a combination of Clutches and Brakes, which are controlled by solenoid valves. Front brake solenoid valve is controlled by the TCM in response to signals sent from the inhibitor switch, vehicle speed sensor and accelerator pedal position sensor (throttle position sensor). Gear will then be shifted to the optimum position.

This is not only caused by electrical malfunction (circuit open or shorted) but also by mechanical malfunction such as control valve sticking, improper solenoid valve operation.

Fig 1) Fr/B Solenoid Valve Operation

Fig 2) Signal Waveform at IDLE

Fig 3) Signal Waveform at accelleration