Honda Civic. Manual — part 183

Fig. 57: Torque Converter Clutch Lock-Up Off Diagram (Disengaging Torque
Converter Clutch)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

No Lock-up

The PCM turns shift solenoid valve D OFF. The lock-up shift valve is on the right
side, and uncovers the torque converter pressure port leading to the back of the
torque converter. Torque converter pressure (92) regulated by the regulator valve
flows to the lock-up shift valve, and becomes torque converter pressure (94).
Torque converter pressure (94) enters into the back of the torque converter, and
discharges into the circuit from the front of the torque converter. When the
hydraulic pressure flow enters the torque converter from the rear and discharges it
from the front, the torque converter clutch piston and cover become disengaged.
This is called the non lock-up condition.

NOTE:

When used, "left" or "right" indicates direction on the
hydraulic circuit.

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)

Fig. 58: Hydraulic Fuel Pressure Flow Diagram (No Lock-Up)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Partial Lock-up

As the speed of the vehicle reaches the programmed value, the PCM turns shift
solenoid valve D ON. Shift solenoid valve D pressure (SD) is applied to the right
end of the lock-up shift valve, which switches the pressure over to the torque
converter pressure port leading to the front of the torque converter. Torque
converter pressure (91) enters into the front of the torque converter to engage the
torque converter clutch piston. The PCM also controls A/T clutch pressure control
solenoid valve A to regulate A/T clutch pressure control solenoid valve A pressure
(55), and A/T clutch pressure control solenoid valve A pressure (55) is applied to
the lock-up control valve. Torque converter pressure (94) drained from the back of
the torque converter is applied to the right side of the lock-up control valve, and

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)

torque converter pressure (90) is applied to the left side of the lock-up control valve.
The lock-up control valve controls the lock-up volume, by receiving these
pressures. The torque converter clutch is engaged partially during torque converter
pressure (90) in the left side of the lock-up control valve is higher, and the torque
converter clutch is engaged securely according to the volume of pressure in the
right side of the lock-up control valve. Under this condition, the torque converter
clutch is engaged by pressure entering into the front side of the torque converter;
this condition is partial lock-up.

Fig. 59: Hydraulic Fuel Pressure Flow Diagram (Partial Lock-Up)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

NOTE:

When used, "left" or "right" indicates direction on the
hydraulic circuit.

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)

Full Lock-up

When the vehicle speed increases, the PCM controls A/T clutch pressure control
solenoid valve A to increase A/T clutch pressure control solenoid valve A pressure
(55). A/T clutch pressure control solenoid valve A pressure (55) is applied to the
lock-up control valve, and the lock-up control valve is moved to the left side to
release torque converter back pressure (94). Torque converter pressure (91) enters
into the front of the torque converter, and the torque converter clutch piston is
engaged with the torque converter cover securely by torque converter pressure.
Under this condition, torque converter back pressure is released fully, causing the
torque converter clutch to be fully engaged; this condition is full lock-up.

NOTE:

When used, "left" or "right" indicates direction on the
hydraulic circuit.

2008 Honda Civic LX

2006-08 TRANSMISSION Automatic Transmission - Civic (Except Hybrid)