2005 SCION tC (EWD572U)
126
ECT and A/T Indicator
Previous automatic transaxle have selected each gear shift using the mechanically controlled throttle hydraulic pressure,
governor hydraulic pressure and lock–up hydraulic pressure. The electronically controlled transmission, however, electrically
controls the line pressure and lock–up pressure etc., through the solenoid valve. Engine control module controls each
solenoid valve based on the input signals from each sensor, which makes smooth driving possible by shift selection for each
gear that is most appropriate to the driving conditions at that time.
1. Gear Shift Operation
When driving, the engine warm up condition is input as a signal to TERMINAL THW of the engine control module from the
engine coolant temp. sensor and the vehicle speed signal is input to TERMINAL SPD of the engine control module. At the
same time, the throttle valve opening signal from throttle body assembly is input to TERMINALS VTA1 and VTA2 of the
engine control module as throttle angle signal.
Based on these signals, the engine control module selects the best shift position for the driving conditions and sends current
to the electronically controlled transmission solenoid.
2. Lock–Up Operation
When the engine control module judges from each signal that lock–up operation conditions have been met, current flows
from TERMINAL S4 of the engine control module to TERMINAL 8 of the electronically controlled transmission solenoid to
GROUND, causing continuity to the lock–up solenoid and causing lock–up operation.
3. Clutch Pressure Control
The electronically controlled transmission solenoid is controlled by the current from TERMINAL SLT+ of the engine control
module, and controls the accumulator hydraulic pressure.
As a result, the clutch to hydraulic pressure is adjusted precisely, and allows stable shift change.
4. Line Pressure Control
The engine control module adjusts the line hydraulic pressure to the optimal level by controlling TERMINAL SLT+ of the
module according to the engine torque data. This realizes the smooth gear shifting.
5. Shifting Control in Uphill/Downhill Traveling
This system determines whether the vehicle is traveling on an incline or decline from the throttle opening angle, vehicle
acceleration condition and brake pedal operation, and controls the shift up to O/D to allow smooth driving.
6. Clutch to Clutch Control
When shifting from the 1st gear to the 2nd gear and the 2nd gear to the 3rd gear, the current from the engine control module
TERMINALS SL1+ and SL2+ control the electronically controlled transmission solenoid, to control the drain orifice hydraulic
pressure (Switch orifice). The electronically controlled transmission solenoid is also controlled by the current from the engine
control module TERMINALS SL1+ and SL2+, to adjust the hydraulic pressure precisely, which ensures smooth shifting.
7. Stop Lamp SW Circuit
If the brake pedal is depressed (Stop lamp SW on) when driving in lock–up condition, a signal is input to TERMINAL STP of
the engine control module, the engine control module operates and continuity to the lock–up solenoid is cut.
E4 (A), E5 (B), E6 (C), E7 (D), E8 (E) Engine Control Module
(A) 9–Ground : Approx. 12 volts with the ignition SW at ON position
(B) 6, (A) 3–Ground : Always approx. 12 volts
(A)15, (C) 1, (C) 4, (C) 7, (D) 7, (E) 6, (E) 7–Ground : Always continuity
(B)19–Ground : Approx. 12 volts with the brake pedal depressed
P1 Park/Neutral Position SW
2–1 : Closed with the shift lever in R position
2–7 : Closed with the shift lever in D position
2–3 : Closed with the shift lever in 2 position
2–8 : Closed with the shift lever in L position
2–6 : Closed with the shift lever in P position
2–9 : Closed with the shift lever in N position
System Outline
Service Hints
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