Circuit Description

WARNING: This page is about a different variant/trim than selected.

The throttle pressure that is applied to the primary regulator valve (which modulates line pressure) causes the shift solenoid valve SLT, under electronic control, to precisely and minutely modulate and generate line pressure according to the accelerator pedal effort, or engine power output detected. This controls the line pressure and provides smooth shifting characteristics.

Upon receiving the throttle valve opening angle signal, ECM controls the line pressure by sending a predetermined (*) duty ratio to the solenoid valve, modulating the line pressure, generating throttle pressure. (*) Duty Ratio

The duty ratio is the ratio of the period of continuity in one cycle. For example, if A is the period of continuity in one cycle, and B is the period of non-continuity, then

A Duty Ratio = A/A+B x 100(%)

Fig 1: Solenoid Current Flow Graph

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fail-safe function:

If the gear is in 3rd, the 4th up-shift is prohibited.
If the gear is in 4th, the 3rd down-shift is prohibited. (In case of the output speed is more than 5,000 RPM only.)

Fig 2: Duty Ratio Cycle Graph

NOTE: Refer to the chart for the waveform between terminals SLT⁺ and SLT^- during engine idling.

Fig 3: Waveform Chart Between Terminals SLT+ And SLT-