1995 ACURA TL Service Repair Manual

Electronic Control System

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.ProCarManuals.com

Description
Electronic Contro l Syste m (cont'd )
Lock-up Contro l
From senso r inpu t signals , th e PC M determine s whethe r t o tur n th e lock-u p O N o r OFF , an d activate s lock-u p contro l
solenoi d valv e A and/o r B accordingly .
Th e combinatio n o f drivin g signal s t o lock-u p contro l solenoi d valve s A an d B is show n in th e tabl e below .
Shif
t Contro l
Th e PC M
instantaneously determine s whic h gea r shoul d b e selecte d b y variou s signal s sen t fro m sensors , an d i t actuate s
th e shif t contro l solenoi d valve s A an d B to contro l shifting . Also , a Grad e Logi c Contro l Syste m ha s bee n adopte d to contro l
shifting in positio n whil e th e vehicl e is ascendin g o r descendin g a slope , o r reducin g speed .
Shif t contro l solenoi d valv e
Positio n (gear )
(1st)
A
OFF
(2nd )
(3rd)
(4th)
(2nd )
(1st)
(Reverse )
ON
O N
OF F
ON
OF F
ON
B
O N
O N
OF F
OF F
ON
O N
OF F
Dut y operatio n
ONOF FON
O N
AB
OF F
OF F
ON
O N
OF F
ON
ON
Lock-u p contro l solenoi d valv e
Lock-u p conditio n
Lock-u p OF F
Lock-up , sligh t
Lock-up , hal f
Lock-up , ful l
Lock-u p
during deceleratio n
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Grade Logic Control System

How it works:

The PCM compares actual driving conditions with driving conditions memorized in the PCM, based on the input from the

vehicle speed sensor, throttle position sensor, engine coolant temperature sensor, barometric pressure sensor, brake

switch signal and shift lever position signal, to control shifting while a vehicle is ascending or descending a slope, or

reducing speed.

(cont'd)ProCarManuals.com

Description
NOTE:
Shift schedule s betwee n 3r d an d 4t h gea r store d i n th e PC M enabl e th e PCM' s fuzz y logi c t o automaticall y selec t th e
mos t suitabl e gea r accordin g t o th e magnitud e o f a gradient .
Fuzz y logi c i s a for m o f artificia l intelligenc e tha t let s computer s respon d t o changin g condition s muc h lik e a huma n
mind would .
Descendin g Contro l
whe n th e throttl e is close d become s faste r tha n th e se t spee d fo r fla t roa d drivin g t o wide n th e 3r d gea r drivin g area .
This, i n combinatio n wit h engin e brakin g fro m th e deceleratio n lock-up , achieve s smoot h drivin g whe n th e vehicl e is
descending .
Ther e ar e tw o descendin g mode s wit h differen t 3r d gea r drivin g area s accordin g t o th e magnitud e o f a gradien t store d i n
th e PCM .
When th e vehicl e is in 4t h gear , an d yo u ar e deceleratin g o n a gradua l hill , o r whe n yo u ar e applyin g th e brake s o n a stee p
hill, the transmissio n will downshif t to 3r d gear . Whe n you accelerate , the transmissio n will the n retur n to 4t h gear .
Electroni c Contro l Syste m (cont'd )
Ascendin g Contro l
3r d gea r t o preven t th e transmissio n fro m frequentl y shiftin g betwee n 3r d an d 4t h gears , s o th e vehicl e ca n ru n smoot h
an d hav e mor e powe r whe n needed . position
, th e syste m extend s th e engagemen t are a o f
Whe n th e PC M determine s tha t th e vehicl e i s climbin g a hil l i n
ASCENDIN G MOD E DESCENDIN G MOD E
Deceleratio n Contro l
Whe n th e vehicl e goe s aroun d a corner , an d need s to decelerat e firs t an d the n accelerate , th e PC M set s th e dat a fo r deceleratio n
contro l t o reduc e th e numbe r o f time s th e transmissio n shifts . Whe n th e vehicl e i s deceleratin g fro m speed s abov e 3 0 mp h
(4 8 km/h) , th e PC M shift s th e transmissio n fro m 4t h to 2n d earlie r tha n norma l t o cop e wit h upcomin g acceleration .
Whe
n th e PC M determine s tha t th e vehicl e i s goin g dow n a hil l i n position , th e shift-u p spee d fro m 3r d t o 4t h gea r
3RD/4T H SHIFTIN GCHARACTERISTIC SCONTROL ARE A
Flat roa dmod e
. Stee p descendin gmode
Gradua l descendin gmode
Vehicl e spee dmph (km/h )Vehicle spee dmph (km/h )
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Description

The hydraulic control system is controlled by the ATF pump, valves, and accumulators in the valve bodies. The ATF pump

is driven by splines on the end of the torque converter which is attached to the engine.

Fluid from the ATF pump flows through the regulator valve to maintain specified pressure through the main valve body to

the manual valve, directing pressure to each of the clutches.

The valve body includes the main valve body, the secondary valve body, the ATF pump body, the regulator valve body,

the throttle valve body, and the accumulator body. The throttle valve body is joined with the linear solenoid.

The shift control solenoid valves A and B are bolted to the secondary valve body. The lock-up control solenoid valve assem-

bly is bolted to the outside of the torque converter housing.

ATF PUMP BODY

ACCUMULATOR BODY

SHIFT CONTROL

SOLENOID VALVE

A/B

REAR COVER

REGULATOR VALVE

BODY

THROTTLE VALVE BODY

SECONDARY VALVE BODY

MAIN VALVE BODY

ATF PASSAGE

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

Hydraulic Control/Lower Valve Body Assembly — '96 Model

The lower valve body assembly is located on the bottom of the transmission housing. The lower valve body assembly

consists of the main valve body, the secondary valve body, and the ATF passage.

Main Valve Body

The main valve body houses 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 primary functions of the main valve body are to switch fluid pressure on and off, and to control the hydraulic pressure

going to the hydraulic control system.

Secondary Valve Body

The secondary valve body is located on the main valve body. The secondary valve body houses the modulator valve, the

3-4 orifice control valve, the 4-3 shift timing valve, the 1st accumulator piston, and the 2nd accumulator piston. The shift

control solenoid valves A and B are bolted to the secondary valve body.

Throttle Valve Body/Linear Solenoid

The throttle valve body is joined with the linear solenoid, which is controlled by the PCM. The throttle valve body/linear

solenoid assembly is located on the secondary valve body. The throttle valve body houses the throttle valve.

SHIFT CONTROL

SOLENOID VALVE B

SHIFT CONTROL

SOLENOID VALVE A

MODULATOR VALVE

1ST ACCUMULATOR

PISTON

SECONDARY VALVE

BODY

MAIN VALVE BODY

MANUALVALVE

CPC VALVE
LINEAR SOLENOID

THROTTLE VALVE BODY

THROTTLE VALVE

2ND ACCUMULATOR

PISTON

3-4 ORIFICE CONTROL

VALVE

4-3

SHIFT TIMING VALVE

4-3 KICK-DOWN

VALVE

3-4 SHIFT VALVE

2-3 SHIR VALVE

1-2 SHIFT VALVE

(cont'd)ProCarManuals.com

Hydraulic Control (cont'd)/Lower Valve Body Assembly — '97 - '98 Models

The lower valve body assembly is located on the bottom of the transmission housing. The lower valve body assembly

consists of the main valve body, the secondary valve body, and the ATF passage.

Main Valve Body

The main valve body houses 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 primary functions of the main valve body are to switch fluid pressure on and

off, and to control the hydraulic pressure going to the hydraulic control system.

Secondary Valve Body

The secondary valve body is located on the main valve body. The secondary valve body houses the line pressure control

valve, the modulator valve, the 3-4 orifice control valve, the 4-3 shift timing valve, the 1st accumulator piston, and the 2nd

accumulator piston. The shift control solenoid valves A and B are bolted to the secondary valve body.

Throttle Valve Body/Linear Solenoid

The throttle valve body is joined with the linear solenoid, which is controlled by the PCM. The throttle valve body/linear

solenoid assembly is located on the secondary valve body. The throttle valve body houses the throttle valve.

LINE PRESSURE

CONTROL VALVE

LINEAR SOLENOID

SHIFT CONTROL

SOLENOID VALVE B

SHIFT CONTROL

SOLENOID VALVE A

MODULATOR VALVE

1ST ACCUMULATOR

PISTON

SECONDARY VALVE

BODY

MAIN VALVE BODY

MANUAL VALVE

MAIN ORIFICE CONTROL VALVE
THROTTLE VALVE BODY

THROTTLE VALVE

2ND ACCUMULATOR

PISTON

3-4 ORIFICE CONTROL

VALVE

4-3

SHIFT TIMING VALVE

4-3 KICK-DOWN

VALVE

3-4 SHIFT VALVE

2-3 SHIFT VALVE

1-2 SHIFT VALVE
DescriptionProCarManuals.com

Hydraulic Control

ATF Pump Body

The ATF pump body is located on the torque converter housing. The ATF pump body consists of the ATF pump gears, the

relief valve, the lock-up control valve, the lock-up timing valve, and the torque converter check valve. The torque converter

check valve is located between the ATF pump body and the torque converter housing.

Accumulator Body

The accumulator body is located on the torque converter housing next to the ATF pump body. The accumulator body

houses the 3rd accumulator piston and the 4th accumulator piston.

Regulator Valve Body

The regulator valve body is located on the ATF pump body. The regulator valve body consists of the regulator valve, the

cooler relief valve, and the lock-up shift valve.

REGULATOR VALVE

BODY

4TH ACCUMULATOR
REGULATOR VALVE

3RD ACCUMULATOR
ATF PUMP BODY

RELIEF VALVE

TORQUE CONVERTER

CHECK VALVE
LOCK-UP CONTROL

VALVE

LOCK-UP TIMING

VALVE

COOLER RELIEF

VALVE

ACCUMULATOR BODY

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

(cont'd)ProCarManuals.com