clutch ACURA TL 1995 Service Repair Manual

PGM-FI System

System Description (cont'd)

3. Fuel Cut-off Control

During deceleration with the throttle valve closed, current to the fuel injectors is cut off to improve fuel economy at

speeds over 1,000 rpm.

Fuel cut-off action also takes place when engine speed exceeds 6,500 rpm, regardless of the position of the throttle

valve, to protect the engine from over-revving.

4. A/C Compressor Clutch Relay .

When the PCM receives a demand for cooling from the air conditioning system, it delays the compressor from being

energized, and enriches the mixture to assure a smooth transition to the A/C mode.

5. Evaporative Emission (EVAP) Purge Control Solenoid Valve

'96 model: When the engine coolant temperature is below 158°F (70°C), the PCM controls the EVAP purge control

solenoid valve which cuts vacuum to the EVAP purge control canister diaphragm.

'97 - 98 models: When the engine coolant temperature is above 99°F (37°C), the PCM controls the EVAP purge control

solenoid valve which controls vacuum to the EVAP purge control canister.

6. Intake Air Bypass (IAB) Low Control Solenoid Valve, Intake Air Bypass (IAB) High Control Solenoid Valve

When engine speed is below 3,350 rpm, the IAB High Control Solenoid Valve and IAB Low Control Solenoid Valve are

activated by a signal from the PCM. Intake air flows through a long chamber path, increasing torque at low RPM.

When engine speed is 3,350 - 3,950 rpm, the IAB Low Control Solenoid Valve is deactivated by the PCM. Intake air

flows through a short chamber path, increasing mid-range torque.

When the engine rpm is above 3,950 rpm, the IAB Low Control Solenoid Valve and IAB High Control Solenoid Valve are

deactivated by the PCM. This creates a very short intake path and increases high-speed torque.

7. Exhaust Gas Recirculation (EGR) Control Solenoid Valve

When the EGR is required for control of oxides of nitrogen (NOx) emissions, the PCM controls the EGR control solenoid

valve which supplies regulated vacuum to the EGR valve.

ECM Fail-safe/Back-up Functions

1. Fail-safe Function

When an abnormality occurs in a signal from a sensor, the PCM ignores that signal and assumes a pre-programmed

value for that sensor that allows the engine to continue to run.

2. Back-up Function

When an abnormality occurs in the PCM itself, the fuel injectors are controlled by a back-up circuit independent of the

system in order to permit minimal driving.

3. Self-diagnosis Function [Malfunction Indicator Lamp (MIL)]

When an abnormality occurs in a signal from a sensor, the PCM supplies ground for the MIL and stores the DTC in

erasable memory. When the ignition is initially turned on, the PCM supplies ground for the MIL for two seconds to

check the MIL bulb condition.

4. Two Driving Cycle Detection Method

To prevent false indications, the two driving cycle detection method is used for the H02S, fuel metering-related, idle

control system, ECT sensor, EGR system, TWC, EVAP control system and other self-diagnostic functions. When an

abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after the ignition switch is

turned OFF and ON (II) again, the PCM informs the driver by lighting the MIL.

However, to ease troubleshooting, this function is cancelled when you short the service check connector. The MIL will

then blink immediately when an abnormality occurs.ProCarManuals.com

(From pag e 11-104 )
I s ther e a clickin g nois e fro m
th e A/ C compresso r clutch ?
Chec k fo r th e operatio n o f th e
A/C :1. Star t th e engine .
2 . Tur n th e blowe r switc h ON .
3 . Tur n th e A/ C switc h ON .
Doe s th e A/ C operate ?
Ai r conditionin g signa l i s OK . Chec
k fo r a n ope n i n th e wir e
(ACC line) :Momentaril y connec t th e A/ C
clutc h rela y 4 P connecto r termi -
nal No . 2 to bod y groun d wit h ajumpe r wir e severa l times . A/
C CLUTC H RELA Y CONNECTO R (C308 )
JUMPE RWIRE
Wire sid e o f
femal e terminal s
I s ther e a clickin g nois e fro m
th e A/ C compresso r clutch ? Se
e ai r conditione r inspectio n
(se e sectio n 22 ).
Repai r ope n in th e wir e betwee n
th e PC M (A8 ) an d th e A/ C clutc h
relay.
PCM CONNECTOR S
A (26P)
Chec k fo r a n ope n i n th e wir e
(AC S line) :
Measur e voltag e betwee n PC M
connecto r terminal s A2 6 an d C2 . Wir
e sid e o f femal e terminal s
I s voltag e les s tha n 1. 0 V ? Repai
r ope n i n th e wir e betwee n
th e PC M (C2 ) an d th e A/ C pres -
sur e switc h A or radiato r fa n
diode .
Substitut e a known-goo d PC M
an d recheck . I f symptom/indi -
catio n goe s away , replac e th e
origina l PCM .
Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
C (12P )
ProCarManuals.com

Description

The automatic transmission is a combination of a 3-element torque converter and a dual-shaft electronically controlled

automatic transmission which provides 4 speeds forward and 1 reverse. The entire unit is positioned in line with the engine.

Torque Converter, Gears and Clutches

The torque converter consists of a pump, turbine, and stator, assembled in a single unit. They are connected to the engine

crankshaft so they turn together as a unit as the engine turns. Around the outside of the drive plate is a ring gear which

meshes with the starter pinion 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 two parallel shafts: the mainshaft and the countershaft. The mainshaft is in line with the engine

crankshaft. The mainshaft includes the 1st, 4th and 2nd clutches and gears for 4th, 1st, 2nd and reverse (3rd gear is integral

with the mainshaft). The countershaft includes the 3rd, 1st-hold and reverse clutches, and gears for 3rd, 4th, 1st, 2nd,

reverse and parking. The secondary drive gear is integrated with the countershaft. The gears on the mainshaft are in con-

stant mesh with those on the countershaft. When certain combinations of gears in the transmission are engaged by clutch-

positions.

and
es, power is transmitted from the mainshaft to the countershaft to provide

Electronic Control

The electronic control system consists of a Powertrain Control Module (PCM), sensors, a linear solenoid and four solenoid

valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions.

The PCM is located below the dashboard, under the front lower panel on the passenger's side.

Hydraulic Control

The lower valve body assembly includes the main valve body, the secondary valve body, the throttle valve body, the lin-

ear solenoid, the shift control solenoid valves and the ATF passage body. They are bolted on the lower part of the trans-

mission housing. The regulator valve body, the ATF pump body, and the accumulator body are bolted to the torque con-

verter housing.

The main valve body on '96 model contains the manual valve, the 1-2 shift valve, the 2-3 shift valve, the 3-4 shift valve, the

4-3 kick-down valve and the Clutch Pressure Control (CPC) valve. The main valve body on '97 model contains the manual

valve, the 1-2 shift valve, the 2-3 shift valve, the 3-4 shift valve, the 4-3 kick-down valve and the main orifice control valve.

The secondary valve body on '96 model contains the 3-4 orifice control valve, the 4-3 shift timing valve, the modulator valve

and the accumulator pistons.The secondary valve body on '97 model contains the 3-4 orifice control valve, the 4-3 shift tim-

ing valve, the line pressure control valve, the modulator valve and the accumulator pistons. The throttle valve body

includes the throttle valve which is bolted onto the secondary valve body. The linear solenoid is joined to the throttle valve

body. The regulator valve body contains the regulator valve, the lock-up shift valve and the cooler relief valve. Fluid from

the regulator passes through the manual valve to the various control valves. The ATF pump body contains the lock-up tim-

ing valve, the lock-up control valve and the relief valve. The torque converter check valve is located in the torque converter

housing under the ATF pump body. The accumulator body contains the accumulator pistons. The reverse accumulator and

the 1st-hold accumulator pistons are assembled in the rear cover.

The 1st, 1st-hold, 2nd and reverse clutches receive fluid from their respective feed pipes, and the 3rd and 4th clutches

receive fluid from the internal hydraulic circuit.

Shift Control Mechanism

Input from various sensors located throughout the vehicle determines which shift control solenoid valve the PCM will acti-

vate. Activating a shift control solenoid valve changes modulator pressure, causing a shift valve to move. This pressurizes a

line to one of the clutches, engaging the clutch and its corresponding gear.

er through a fluid passage, causing the lock-up 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 hydraulic control, the PCM optimizes the tim-

ing of the lock-up mechanism. The lock-up valves control the range of lock-up according to lock-up control solenoid valves

A and B, and throttle valve. When lock-up control solenoid valves A and B activate, modulator pressure changes. The lock-

up control solenoid valves A and B are mounted on the torque converter housing, and are controlled by the PCM.

(cont'd)
Lock-up Mechanism

In
position, in 2nd, 3rd, and 4th, and
position in 3rd, pressurized fluid is drained from the back of the torque convert-ProCarManuals.com

Description
(cont'd)
Front wheel s locked ; parkin g brak e paw l engage d wit h parkin g gea r o n countershaft . Al l clutche s
released .
Reverse ; revers e clutc h engaged .
Al l clutche s released .
Automati c Transaxl e (A/T ) Gea r Positio n Indicato r
Th e A/ T gea r positio n indicato r i n th e instrumen t pane l show s whic h gea r ha s bee n selecte d withou t havin g t o loo k dow n
a t the c onsole .
position s throug h th e us e o f a slide-type , neutral-safet y switch .Starting i s possibl e onl y i nan d
Gea r Selectio n
Th e shif t leve r ha s seve n positions :
3r d gea r ranges . 1s
t gear .
2n d gea r an d
PARK ,REVERSE ,NEUTRAL,1st throug h 4t h gea r ranges .1st throug h
For rapi d acceleratio n a t highwa y speed s an d genera l driving ; up-hil l an d down-hil l driving ; start s of f
i n 1st , shift s automaticall y t o 2nd , the n 3rd , dependin g o n vehicl e spee d an d throttl e position .
Downshift s throug h 2n d to
1st o n deceleratio n t o stop . Th e lock-u p mechanis m come s int o operatio n
i n 3r d speed .
Fo r engin e brakin g o r bette r tractio n startin g of f o n loos e o r slipper y surfaces ; stay s i n 2n d gear ,
doe s no t shif t u p o r down .
Fo r engin e braking ; stay s i n 1s t gear , doe s no t shif t up .
Genera
l driving ; start s of f i n 1st , shift s automaticall y t o 2nd , 3rd , the n 4th , dependin g o n vehicl e
spee d an d throttl e position . Downshift s throug h 3rd , 2n d an d 1s t o n deceleratio n t o stop . Th e lock -
u p mechanis m come s int o operatio n i n positio n in 2nd , 3r d an d 4t h gear .
ProCarManuals.com

ATF DIPSTICK

RING GEAR

TORQUE

CONVERTER

4TH CLUTCH

1ST CLUTCH

2ND CLUTCH

MAINSHAFT

COUNTERSHAFT
EXTENSION

SHAFT

SECONDARY

DRIVEN GEAR

3RD CLUTCH

REVERSE

CLUTCH
1ST-HOLD

CLUTCH
DIFFERENTIAL

ASSEMBLY

NOTE: The illustration shows '96 model; '97 - '98 models are similar.ProCarManuals.com

Description

Clutches

The four-speed automatic transmission uses hydraulically-actuated clutches to engage or disengage the transmission gears.

When the hydraulic pressure is introduced into the clutch drum, the clutch piston moves. This presses the friction discs

and steel plates together, locking them so they don't slip. Power is then transmitted through the engaged clutch pack to its

hub-mounted gear.

Likewise, when the hydraulic pressure is bled from the clutch pack, the piston releases the friction discs and steel plates, and

they are free to slide past each. This allows the gear to spin independently of its shaft, transmitting no power.

1st Clutch

The 1st clutch, engages/disengages 1st gear, and is located at the middle of the mainshaft. The 1st clutch is joined back-to-

back to the 4th clutch. The 1st clutch is supplied hydraulic pressure by its ATF feed pipe within the mainshaft.

shaft. The 1st-hold clutch is supplied hydraulic pressure by its ATF feed pipe within the countershaft.
1st-hold Clutch

The 1st-hold clutch engages/disengages 1st-hold,
position or
position, and is located at the middle of the counter-

2nd Clutch

The 2nd clutch engages/disengages 2nd gear, and is located on the rear end of the mainshaft. The 2nd clutch is supplied

hydraulic pressure by its ATF feed pipe within the mainshaft.

3rd Clutch

The 3rd clutch engages/disengages 3rd gear, and is located at the end of the countershaft, opposite the rear cover. The

3rd clutch is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.

4th Clutch

The 4th clutch engages/disengages 4th gear, and is located at the middle of the mainshaft. The 4th clutch is joined back-

to-back to the 1st clutch. The 4th clutch is supplied hydraulic pressure by a circuit connected to the internal hydraulic cir-

cuit.

Reverse Clutch

The reverse clutch engages/disengages reverse gear, and is located on the rear end of the countershaft. The reverse clutch is

supplied hydraulic pressure by its ATF feed pipe within the countershaft.

One-way Clutch

This transmission has two one-way clutches: the 1st gear one-way clutch and the 2nd gear one-way clutch. The 1st gear

one-way clutch is positioned between the countershaft 1st gear and the one-way clutch hub, with the one-way clutch hub

splined to the countershaft 2nd gear. The countershaft 1st gear provides the outer race surface, and the one-way clutch

hub provides the inner race surface. The 2nd gear one-way clutch is positioned between the countershaft 2nd gear and

the parking gear, with the parking gear splined to the countershaft. The countershaft 2nd gear provides the outer race sur-

face, and the parking gear provides the inner race surface. The one-way clutches lock up when power is transmitted from

the mainshaft 1st gear to the countershaft 1st gear. The 2nd gear one-way clutch locks up when power is transmitted from

the mainshaft 2nd gear to the countershaft 2nd gear.

The 1st clutch and gears remain engaged in the 1st, 2nd, 3rd, and 4th gear positions in the

the 1st gear one-way clutch disengages when the 2nd, 3rd, or 4th clutches/gears are applied in the

The sprags engage/

disengage outside

and inside of the

one-way clutch.
is because the increased rotational speed of the gears on the countershaft over-ride the locking "speed range" of the one-

way clutch. Thereafter, the one-way clutch freewheels with the 1st clutch still engaged.

INSIDE OF ONE-WAY

CLUTCH

Splined with counter-

shaft
OUTSIDE OF ONE-WAY

CLUTCH
position. However,
or

or

position. ThisProCarManuals.com

MAINSHAFT 3RD
GEAR
MAINSHAFT 4TH
GEA R
4TH CLUTCH
1ST CLUTCH
MAINSHAFT 1STGEAR
MAINSHAFT 2NDGEAR
2ND CLUTCH
MAINSHAF T REVERS EGEAR
DIFFERENTIA L
EXTENSIO N SHAF T
SECONDAR Y DRIV E
GEAR
3RD CLUTC H
SECONDAR Y DRIVE N GEA R
COUNTERSHAF T 3R D
GEA R
COUNTERSHAF T 4T HGEA R
1ST-HOL D CLUTC H
1ST-GEA R ONE-WA Y
CLUTC H
COUNTERSHAF T 1S T GEA R
ONE-WA Y CLUTC H HU B
COUNTERSHAF T 2N D GEA R
2ND-GEA R ONE-WA Y
CLUTC H
PARKIN G GEA R
REVERS E CLUTC H
COUNTERSHAF T REVERS E
GEAR
MAINSHAF T COUNTERSHAF T
NOTE: Th e illustratio n show s '9 6 model ; '9 7 - '9 8 model s ar e similar .
FRONT
ProCarManuals.com

Description

Power Flow

*1: Although the 1st clutch engages, driving power is not transmitted
as
the 1st gear one-way clutch slips.

*2: Although the 1st and 2nd clutches engage, driving power is not transmitted as the one-way clutches slip.

*3: The one-way clutch engages when accelerating, and slips when decelerating.ProCarManuals.com

Position
Hydrauli c pressur e i s no t applie d t o th e clutches . Powe r i s no t transmitte d t o th e countershaft .
Positio n
Hydrauli c pressur e i s no t applie d t o th e clutches . Powe r i s no t transmitte d t o th e countershaft .
Th e countershaf t i s locke d b y th e parkin g brak e paw l interlockin g th e parkin g gear .
4TH CLUTCH 1ST CLUTCH 2ND CLUTCH
TORQU ECONVERTE R
MAINSHAFT
COUNTERSHAF T
REVERS E
CLUTCH
3RD CLUTCH
2ND GEA RONE-WA Y
CLUTC H
1ST GEA RONE-WA Y CLUTC H
(cont'd)
1ST-HOL DCLUTCH PARKIN
GGEAR
ProCarManuals.com

Description

Power Flow (cont'd)

Position

position, hydraulic pressure is applied to the 1st clutch and the
1st-hold
clutch.

The power flow when accelerating is as follows:

1. The hydraulic pressure is applied to the
1st
clutch on the mainshaft, and power is transmitted via the 1st clutch to the

mainshaft
1st gear.

2. The hydraulic pressure is also applied to the 1st-hold clutch on the countershaft. Power transmitted to the mainshaft

1st gear is conveyed via the countershaft 1st gear to the 1st gear one-way clutch, the 2nd gear one-way clutch, and the

1st-hold clutch. The one-way clutches are used to drive the countershaft, and the 1st-hold clutch drives the counter-

shaft.

3. Power is transmitted to the secondary drive gear, which drives the secondary driven gear.

TORQUE CONVERTER

1ST
CLUTCH

MAINSHAFT

1ST
GEAR

SECONDARY

DRIVE GEAR
MAINSHAFT

COUNTERSHAFT

2ND GEAR

ONE-WAY CLUTCH

1ST GEAR

ONE-WAY CLUTCH

SECONDARY DRIVEN GEAR
COUNTERSHAFT

1ST GEAR
In

1ST-HOLD

CLUTCH
PARKING GEARProCarManuals.com