Honda Civic. Manual — part 168

clutch piston
defective

6. Torque converter

check valve
defective

7. Lock-up shift

valve defective

8. Lock-up control

valve defective

output shaft (countershaft) speed
sensor installation.

Inspect the sensor O-ring for
wear and damage.

Replace the torque converter
assembly.

Check the torque converter
check valve in the regulator
valve body.

Check the lock-up shift valve in
the regulator valve body.

Check the lock-up control valve
in the main valve body.

A/T gear position
indicator does
not indicate shift
lever positions

1. Transmission

range switch
defective or out of
adjustment

2. Shift cable broken

or out of
adjustment

3. Connection

between shift
cable and
transmission or
body worn

Check for a stored DTC, and
check for loose connections.

Inspect the transmission range
switch. If the transmission range
switch is faulty, replace it. If the
transmission range switch is out
of adjustment, adjust it and the
shift cable.

Check for a loose shift cable at
the shift lever and the
transmission control lever.

Speedometer and
odometer do not
work

Output shaft
(countershaft) speed
sensor defective

Check for a stored DTC, and
check for loose connections.

Check the output shaft
(countershaft) speed sensor
installation.

Inspect the sensor O-ring.

Engine does not
rev to high rpm,

Engine rocker arm
defective

Check the engine rocker arms.

2008 Honda Civic LX

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

COMPONENT LOCATION INDEX

and the
transmission
upshifts at low
rpm (engine at
normal operating
temperature)

2008 Honda Civic LX

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

Fig. 16: Identifying Automatic Transmission Component Location
Courtesy of AMERICAN HONDA MOTOR CO., INC.

SYSTEM DESCRIPTION

General Operation

The automatic transmission is a combination of a three-element torque converter
and triple-shaft electronically controlled unit which provides five speeds forward
and one in reverse. The entire unit is positioned in line with the engine.

Torque Converter, Shafts, Gears, and Clutches

The torque converter consists of a pump, turbine, and stator assembly in a single
unit. The converter housing (pump) is connected to the engine crankshaft and turns
as the engine runs. Around the outside of the torque converter is a ring gear which
meshes with the starter drive gear when the engine is being started. The entire
torque converter assembly serves as a flywheel while transmitting power to the
transmission mainshaft. The transmission has three parallel shafts; the mainshaft,
the countershaft, and the secondary shaft. The mainshaft is in line with the engine
crankshaft, and includes the 3rd and 5th clutches, and gears for 3rd, 5th, reverse,
and idler. The mainshaft reverse gear is integral with the mainshaft 5th gear. The
countershaft includes the gears for 1st, 2nd, 3rd, 4th-5th, reverse, park, and the final
drive. The countershaft 4th-5th gear enables the shared use of the secondary shaft
4th gear and the mainshaft 5th gear. The countershaft 4th-5th gear and the
countershaft reverse gear can be locked to the countershaft providing the 4th, 5th or
reverse gear, depending on which way the selector is moved. The final drive gear is
integral with the countershaft. The secondary shaft includes the 1st, 2nd, and 4th
clutches, and gears for 1st, 2nd, 4th, and idler. The idler gear shaft is located
between the mainshaft and the secondary shaft, and the idler gear transmits power
between the mainshaft and the secondary shaft. The gears on the mainshaft and the
secondary shaft are in constant mesh with those on the countershaft. When certain
combinations of gears in the transmission are engaged by the clutches, power is
transmitted through the mainshaft, then to the secondary shaft to the countershaft,
or through the mainshaft to the countershaft to provide drive.

Electronic Control

2008 Honda Civic LX

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

The electronic control system consists of the powertrain control module (PCM),
sensors, and seven solenoid valves. Shifting and lock-up are electronically
controlled for comfortable driving under all conditions. The PCM is located in the
engine compartment.

Hydraulic Control

The valve bodies include the main valve body, the regulator valve body, and the
servo body. They are bolted to the torque converter housing. The main valve body
contains the manual valve, cut valve B, shift valves A, C, and D, the relief valve,
the lock-up control valve, the cooler check valve, the servo control valve, and the
ATF pump gears. The regulator valve body contains the regulator valve, the torque
converter check valve, the lock-up shift valve, the 1st accumulator, and the 3rd
accumulator. The servo body contains the servo valve, shift valve B, cut valve A,
the accumulators for 2nd, 4th, and 5th, and shift solenoid valves A, B, C, and D.
Fluid from the regulator passes through the manual valve to the various control
valves. The 2nd, 3rd, and 4th clutches receive fluid from their respective feed pipes,
and the 1st and the 5th clutches receive fluid from the internal hydraulic circuit.

Shift Control Mechanism

To shift gears, the PCM controls shift solenoid valves A, B, C, and D, and A/T
clutch pressure control solenoid valves A, B, and C, while receiving input signals
from various sensors and switches located throughout the vehicle. The shift
solenoid valves shift the positions of the shift valves to switch the port to send
hydraulic pressure to the clutch. A/T clutch pressure control solenoid valves A, B,
and C regulate their respective pressure, and pressurize the clutches to engage them
and their corresponding gears.

Lock-up Mechanism

The lock-up mechanism operates in D (1st, 2nd, 3rd, 4th, and 5th gears), and D3
(1st, 2nd and 3rd gears). The pressurized fluid is drained from the back of the
torque converter through a fluid passage, causing the torque converter clutch piston
to be held against the torque converter cover. As this takes place, the mainshaft
rotates at the same speed as the engine crankshaft. Together with the hydraulic
control, the PCM optimizes the timing and the volume of the lock-up mechanism.
When shift solenoid valve D is turned on by the PCM, shift solenoid valve D

2008 Honda Civic LX

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