Acura 3.5 RL Manual page 506

Description
Lock-up System (cont'd)
Half Lock-up
Torque Converter Clutch (Lock-up Control) Solenoid Valve A: ON Torque Converter Clutch (Lock-up Control) Solenoid
Valve B: ON
The modulator pressure is released by the solenoid valve B, causing the modulator pressure in the left side of the lock-up
control valve to lower.
Also the modulator pressure in the left cavity of the lock-up timing valve is low. However, throttle B pressure is still low at
this time; consequently, the lock-up timing valve is kept on the right side by the spring force.
With the torque converter clutch solenoid valve B turned on, the lock-up control valve is moved somewhat to the left side,
causing the back pressure (F2) to lower. This allows a greater amount of the fluid (F1) to work on the lock-up clutch so as
to engage the clutch. The back pressure (F2) which still exists prevents the clutch from engaging fully.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.