66 CAMRY — NEW FEATURES

 A541E AUTOMATIC TRANSAXLE

1. Description
The A541E automatic transaxle is used in the ’94 model year. It is based on the A540E automatic transaxle used in
the ’93 model year, with the following changes made to match the brand new 1 MZ–FE engine.

 Adopts an Electronically Controlled Transaxle with an intelligent control system, which is a version which has
evolved from the previous Electronically Controlled Transaxle system.

 The hydraulic pressure control has been revised in accordance with the adoption of the above mentioned system.
 The torque converter clutch and the gear train have been revised to match the 1MZ–FE engine.

Specifications

Model ’94 Camry ’93 Camry

Transmission Type
A541E A540E
Item
1st 2.810 ←
2nd 1.549 ←
Gear Ratio 3rd 1.000 ←
Overdrive Gear 0.735 0.734
Reverse 2.296 ←
Counter Gear Ratio 0.945 1.027
Differential Gear Reduction Ratio 3.393 ←
Fluid Capacity Transmission 6.8 (7.2, 5.9) 6.5 (6.9, 5.7)
liters
(US qts, Imp.qts) Differential 0.9 (0.9, 0.8) 0.8 (0.8, 0.7)

Fluid Type ATF Type ←

DEXRONII
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2. Torque Converter Clutch

The torque converter clutch is newly designed to optimally match the brand–new 1MZ–FE engine. It has optimally
designed fluid passages and impeller configuration resulting in substantially enhanced torque ratio and transmission
efficiency to ensure better starting, acceleration and fuel economy, Furthermore, a hydraulically operated lock–up
mechanism which cuts power transmission losses due to slippage at medium and high speeds is used. The basic
construction and operation are the same as for the A540E for the 93’Camry.

3. Planetary Gear Unit

The planetary gear unit is basically the same in construction and operation as in the A540E automatic transaxle, but
the following items have been changed.

Modifications

Items Contents
The number of splines of the clutch that mated with the sun gear drum has
C2 Direct Clutch been changed from 8 to 16 teeth, so that they can perform the function of
a direct clutch speed sensor rotor.
B0 OD Brake The cushion plate has been discontinued for weight reduction.
B1 2nd Coast Brake The brake band width has been changed from 38 mm to 31 mm.
The friction material diameter has been increased to match the increased
B2 2nd Brake
engine power.
The friction material has been reduced from 7 to 6 sheets to reduce drag
torque and for weight reduction.
B3 1st & Reverse Brake
Also, the friction material diameter has been increased to match the
increased engine power.
OD Planetary Gear The gear module has been made compact for quieter operation.
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Specifications

Model ’94 Camry ’93 Camry

Type of Transaxle A541E A540E
Type of Engine
1MZ FE
1MZ–FE 3VZ FE
3VZ–FE
Item
C0 OD Direct Clutch 2 ←
C1 Forward Clutch 5 ←
No of Discs
No.
C2 Direct Clutch 3 ←
B0 OD Brake No. of Discs 3 ←
B1 2nd Gear Brake Band Width (in.) mm 1.22 (31) 1.50 (38)
B2 2nd Brake 4 3
No of Discs
No.
B3 1st & Reverse Brake 6 7
F0 OD One–Way Clutch 24 ←
F1 No. 1 One–Way Clutch No. of Sprags
p g 18 ←
F2 No. 2 One–Way Clutch 32 30
No. of Sun Gear Teeth 39 ←
Front Planetaryy Gear No. of Pinion Gear Teeth 16 ←
No. of Ring Gear Teeth 71 ←
No. of Sun Gear Teeth 27 ←
Rear Planetaryy Gear No. of Pinion Gear Teeth 18 ←
No. of Ring Gear Teeth 62 ←
No. of Sun Gear Teeth 28 22
OD Planetaryy Gear No. of Pinion Gear Teeth 25 18
No. of Ring Gear Teeth 78 61

4. Hydraulic Control System

General
The hydraulic control system of the A541E consists of an oil pump, valve body, solenoid valves, accumulators and
clutches and brakes of the planetary gear unit, as in the A540E for the ’93 Camry. However, the construction and
operation of valve body and solenoid valves, etc. differ from the A540E because the A541E has electronic modulation
of accumulator back pressure control.
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Construction and Operation

1) Valve Body
a. Outline
The valve body consists of the upper and lower valve bodies which contain valves that control fluid pressure
and switch fluid flow from one passage to another.
 Solenoid modulator valve
 Shift solenoid valve SLN
Also, the 1–2, 2–3, and 3–4 shift valves are now made of aluminum for weight reduction.
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Upper Valve Body

Lower Valve Body

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b. Function
Each valve has the following functions:

No. Component Function

It switches hydraulic circuit of line pressure being regulated by the primary
(1) Manual Valve
regulator valve, depending on the transaxle shift lever position.
Using throttle pressure, it regulates hydraulic pressure (generated by the oil
pump) to the line pressure appropriate for the engine load. When the engine
Primary Regulator
(2) load is heavy, it increases line pressure and implements positive engagement of
Valve
clutches and brakes, and when the engine is under a light load, it lowers line
pressure to reduce shift shock and engine power loss.
It produces throttle pressure, based on line pressure, according to the
(3) Throttle Valve
accelerator pedal depression.
Throttle pressure acts on this plug and reduces the rotational force of the
(4) Down–Shift Plug
throttle cam.
In 2nd, 3rd and OD gear ranges, it regulates cut–back pressure acting on the
primary regulator valve by balancing of line pressure from the 1–2 shift valve
(5) Cut–Back Valve and spring tension. By applying regulated cut–back pressure to the primary
regulator valve, it lowers line pressure to prevent unnecessary power loss from
the oil pump.
Secondary It regulates converter pressure and lubrication pressure by balancing hydraulic
(6)
Regulator Valve pressure from the primary regulator valve against spring tension.
In “2” range it converts line pressure acting on 2nd coast brake (B1) to 2nd
2nd Coast
(7) coast modulator pressure to perform smooth engagement by the accumulator
Modulator Valve
back pressure from the accumulator control valve.
Low Coast In “L” range, it converts line pressure acting on 1st & reverse brake (B3) to
(8)
Modulator Valve low modulator pressure to perform smooth engagement.
In the “2” range 2nd gear, this valve supplies B2 line pressure from the 1–2
(9) 2nd Lock Valve
shift valve to the 2nd coast modulator valve via the B1 orifice control valve.
B1 Orifice In up–shifting from the “2” range 1st gear to 2nd gear, this valve controls the
(10)
Control Valve timing of fluid supply to the 2nd coast brake (B1) to engage it smoothly.
Lock–Up Relay It engages and disengages the lock–up clutch of the torque converter according
(11)
Valve to a fluid pressure signal (line pressure) from the solenoid valve SL.
(12) 1–2 Shift Valve It provides shifting between 1st and 2nd gears.
(13) 2–3 Shift Valve It provides shifting between 2nd and 3rd gears.
(14) 3–4 Shift Valve It provides shifting between 3rd and OD gears.
It operates to smoothly engage the clutches and brakes by controlling back
Accumulator
(15) pressure of B0, B2, C1 and C2 accumulators according to the shift solenoid
Control Valve
valve SLN operation.
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No. Component Function

It serves to maintain stable solenoid pressure acting on the solenoid valves SL
Solenoid
(16) and SLN by balancing line pressure from the primary regulator valve against
Modulator Valve
spring tension.
The functions of each accumulator are the same as in the A540E of the ’93
Accumulators
Camry. However, the C1 accumulator has a hydraulic pressure circuit added to
(17) (C1, C2, C0, B2
so that it can control back pressure by way of the accumulator control valve, in
and B0)
the same way as the C2, B2, and B0 accumulators do.
Shift Solenoid
They operate the 1–2, 2–3 and 3–4 shift valves to perform gear shifting the
(18) Valve No. 1 and
same as in the A540E for the ’93 Camry.
No. 2
Shift Solenoid
(19) This valve switches solenoid pressure into lock–up control pressure.
Valve SL
Shift Solenoid This valve, which has been newly added, modulates solenoid pressure into
(20)
Valve SLN accumulator control pressure.
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5. Electronic Control System

General
The electronic control system of the A541E automatic transaxle, modeled after the A540E, offers the following
changes:

 A linear solenoid valve (Shift Solenoid Valve SLN), which can provide the actuator with a hydraulic pressure
proportional to the value of the current, has been added to produce even smoother shifting characteristics.

 The self–diagnosis functions have been revised to comply with the OBD–II requirements.
 The No. 2 speed sensor has been discontinued. Accordingly, the vehicle speed is detected by way of the No. 1
speed sensor.

S t
System F ti
Function A541E A540E
The optimum shift pattern is selected from two shift patterns
Shift Timing in the ECM* by the pattern select switch. The ECM* sends
 
Control current to the No. 1 and /or No. 2 solenoid valves based on
signals from each sensor and shifts the gear.
The optimum lock–up pattern is selected from two lock–up
patterns in the ECM* by the pattern select switch. The
Lock–Up Timing
ECM* sends current to the shift solenoid valve SL based on  
Control
signals from each sensor and engages or disengages the
lock–up clutch.
Accumulator The ECM* sends signals to shift solenoid valve SLN when
Back Pressure gear shift occurs to temporarily lower the accumulator back  —
Control pressure so that the gear shift is completed smoothly.
When the shift lever is shifted from “N” to “D” range, the
”N” to “D” Squat
gear is temporarily shifted to 2nd or O/D and then to 1st to  
Control
reduce vehicle squat.
Engine Torque Retards the engine ignition timing temporarily to improve
 
Control shift feeling during up or down shifting.
Causes the O/D OFF indicator light to blink to inform the
Self–Diagnosis  
driver when the electrical circuit malfunctions.
Controls other normally operating components, permitting
Fail–Safe continued driving when malfunctions occur in the electrical  
circuit.

* ECM (Engine Control Module)

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Construction
The electronic control system can be broadly divided into 3 groups: the sensors, ECM [Engine ECU] and the
actuators. The shaded portions differ form the A540E.
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System Diagram
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Layout of Components
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Construction and Operation of Main Components

1) Direct Clutch Speed Sensor
The sensor is fitted to the upper transaxle case
cover. It detects revolution of the input shaft
based on revolution of the direct clutch drum.

2) Shift Solenoid Valve SL (For Lock–Up Control)

The shift solenoid valve SL has been changed as illustrated below. The non–lockup line pressure, which used
to be released through the drain port in the previous A540E, is no longer released in the current A541E.
Accordingly, the oil pump load has been reduced.

A541E A540E
3) Shift Solenoid Valve SLN(For Accumulator Back Pressure Modulation)
The newly adopted shift solenoid valve SLN is fitted to the transaxle valve body. In accordance with the amount
of current sent from the ECM to the solenoid coil the shift solenoid valve SLN modulates solenoid pressure into
accumulator control pressure acting on the accumulator control valve in the valve body. The accumulator control
valve modulates accumulator back pressure acting on the accumulator back pressure chamber and 2nd coast
modulator valve according to the pressure.
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Function of ECM [Engine ECU]

The ECM receives signals from various sensors and determines the proper shift and lock–up timing accordingly. In
addition, it regulates hydraulic pressure for smoother gear shifting operation.
In the same way as in the 1MZ–FE engine, the self–diagnosis functions comply with OBD–II requirements.
1) Accumulator Back Pressure Control
During gear shifting, the accumulator temporarily accumulates the line pressure according to a difference
between the line pressure (which acts on the operation chamber of the piston and engages the clutches and brakes
of the planetary gear unit) and the accumulator back pressure acting on the back pressure chamber. The
accumulator then gradually applies the stored line pressure to the clutches and brakes to perform gear shifting
smoothly. In the A541E automatic transaxle, the accumulator back pressure that acts on the back pressure
chamber is controlled electronically.
Therefore, gear shifting is performed smoothly regardless of a fluctuation in the engine torque or a change in
the friction characteristics.
The accumulator back pressure is controlled by the shift solenoid valve SLN fitted to the valve body. The solenoid
valve itself is controlled by the ECM changing the duty ratio to the valve according to the gear shifting mode,
the throttle valve opening angle, the direct clutch drum speed and the vehicle speed.
2) Self–Diagnosis
a. Outline
In the same way as in the engine control system of the 1MZ–FE, the diagnosis function of the A541E electronic
control system also complies with the OBD–II requirements. The following are the main structures of the A541E
automatic transaxle which has been adopted in conjunction with OBD–II:
 Data Link Connector: DLC–3 Added for OBD–II.
 Diagnostic Trouble Code Check Method: Performed by connecting the Toyota hand–held tester to DLC–3.
 Diagnostic Trouble Code: See the next page.
 ECM Memory Items: Freezed Frame Data Added
See page 60 of the 1MZ–FE Engine Section for further information.
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DIAGNOSTIC TROUBLE CODE CHART DIAGNOSTIC TROUBLE CODE CHART

(SAE Controlled) (Manufacturer Controlled)

DTC and DTC and

DTC
Malfunction O/D OFF Freeze (Diagnostic Malfunction O/D OFF Freeze
(Diagnostic
Detection Item Indicator Indicator Frame Data Trouble Detection Item Indicator Indicator Frame Data
Trouble
Lamp Light are Stored Code) No. Lamp Light are Stored
Code) No.
in Memory in Memory
Output Speed “NC2”
Sensor Circuit Revolution
Malfunction Sensor Circuit
P0720 ON Blinking YES P1705 ON Blinking YES
(for Electronic Malfunction
Controlled (Direct Clutch
Transaxle) Speed Sensor)
Shift Solenoid Linear
A Malfunction Solenoid for
P0750 ON Blinking YES
(Shift Solenoid Accumulator
P1765 OFF OFF DTC only
Valve No. 1) Pressure
Control Circuit
Shift Solenoid Malfunction
A Electrical
P0753 ON Blinking YES
(Shift Solenoid
Valve No. 1)
Shift Solenoid
B Malfunction
P0755 ON Blinking YES
(Shift Solenoid
Valve No. 2)
Shift Solenoid
B Electrical
P0758 ON Blinking YES
(Shift Solenoid
Valve No. 2)
Shift Solenoid
E Malfunction
P0770 ON Blinking YES
(Shift Solenoid
Valve SL)
Shift Solenoid
E Electrical
P0773 ON Blinking YES
(Shift Solenoid
Valve SL)
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6. Differential
A 2–pinion type differential has been adopted for
Specifications
weight reduction.
Model
’94 Camry ’93 Camry
Item
Helical
Gear Type
Gear ←
Differential
Speed Gear Ratio
3.933 ←
Reduction
Mechanism Number of teeth
of ring gear and
drive pinion
59/15 ←
gear
Skew
Gear Type
Bevel Gear ←
Operating
Mechanism Number of
2 4
Pinions