1986 TOYOTA CAMRY V20 ECU

INSPECTION ELECTRONIC CONTROL
COMPONENTS
1. INSPECT VOLTAGE OF ECT ECU CONNECTOR
(a) Remove the glove box and instrument panel.
(b) Turn on the ignition switch.
(e) Measure the voltage at each terminal.
Throttle valve fully closed to fully open Throttle valve fully closed to fully open
Throttle valve fully closed to fully open
Vehicle moving (Cruise control OFF)Standing still (Cruise control OFF) Throttle valve opening above 1 .5°
When brake pedal is not depressed When brake pedal is depressed Throttle valve fully closed Throttle valve fully closed
Throttle valve fully closed
Throttle valve fully closed Throttle valve fully open Throttle valve fully open Throttle valve fully openMeasuring condition
Except L range
Except N range Except 2 rangeVoltage (V)
Terminal
N range 2 range
L range
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A140E)AT±32

(Assembly of Valve Body)
(See page AT±121)
1. POSITION PLATE AND NEW GASKETS ON LOWER
VALVE BODY
Position the new No. 2 gasket, the plate and then the new
No. 1 gasket on the lower valve body.
HINT: Since No. 1 gasket and No. 2 gasket are similar use
the illustration below to discriminate between them.
2. PLACE LOWER VALVE BODY WITH PLATE AND
GASKETS ON UPPER VALVE BODY
HINT: Hold the lower valve body, gaskets and plate
securely so they do not separate.
Align each bolt hole in the valve bodies with the gas-
kets and plate.
3. INSTALL AND FINGER TIGHTEN BOLTS IN LOWER
VALVE BODY TO SECURE UPPER VALVE BODY
Install and finger tighten the three bolts.
HINT: Each bolt length (mm (in.)) is indicated in the
figure.
± AUTOMATIC TRANSAXLEComponent Parts (Valve Body) (A140E)AT±130

(A540H)
The A540H automatic transaxle design is based on the A540E automatic transaxle and equipped with
a center differential and transfer.
This transaxle has the same hydraulic multiplate clutch in the center differential limiting control mecha-
nism as the A241 H automatic transaxle on the Corolla All±TRAC/4WD Station Wagon. The fluid pres-
sure acting on the hydraulic multiplate clutch of the A540H is controlled by the ECT ECU (Electronic
Control Unit according to the vehicle driving conditions. As a result, torque is distributed to the front
and rear wheels appropriately at all times to maximize the overall performance of the 4WD vehicle.
NOTICE: Special handling methods are necessary for full±time 4WD vehicles during inspection and mainte-
nance. Instructions concerning these handling methods are given on page IN±8.
± AUTOMATIC TRANSAXLEDescription (A540E and A540H)AT±185

( ) 1: No fail±safe function X: Malfunctions
HINT: (A540H) When any one of the speed sensors (front or rear) or center differential control sole-
noid valves (No. 1 or No. 2) malfunction, the ECT ECU stops center differential control and main-
tains the center differential in a free condition.
Operating Mechanism for Each Gear (A540E A540H)
1. CLUTCH BRAKE AND ONE±WAY CLUTCH
A540E, A540H
Down±shift only ± no up±shift
2. SOLENOID SYSTEM
Possible gear positions in accordance with solenoid operating conditions.
A540E, A540H
NO. 2 SOLENOID
MALFUNCTIONING NO. I SOLENOID
MALFUNCTIONINGBOTH SOLENOIDS
MALFUNCTIONING Shift lever
positionGear position
NORMAL
D rangeParking
2 range
L rangeReverse
Neutral
Range
2nd3 rd
O/D
2nd1st
1st 1st2nd
3rd
± AUTOMATIC TRANSAXLETroubleshooting (Operating Mechanism for Each Gear
(A540E and A540H)AT±189

Diagnosis System
DESCRIPTION
1. A self±diagnosis function is. built into the electrical control
system. Warning is indicated by the overdrive OFF indicator.
HINT: Warning and diagnostic codes can be read only when
the overdrive switch is ON. If OFF, the overdrive OFF
indicator is lit continuously and will not blink.
(a) If a malfunction occurs within the speed sensors or sole-
noids, the overdrive OFF light will blink to warn the driver.
However, there will be no warning of a malfunction with
lock±up solenoid.
W The diagnostic code can be read by the number of
blinks of the overdrive OFF indicator when terminals
Tt and E1 are short±circuited. (See page AT± 191)
(c) The throttle position sensor or brake signal are not indicated,
but inspection can be made by checking the voltage at ter-
minal Tt of the check connector.
(d) The signals to each gear can be checked by measuring the
voltage at terminal Tt of the check connector while driving.
2. The diagnostic (malfunction) code is retained in memory by the
ECU and due to back±up voltage, is not canceled out when the
engine is turned off. Consequently, after repair, it is necessary
to turn the ignition switch off and remove the fuse EFI (15A)
(A540E) or DOME (20A)
(A540H) or disconnect the Engine and ECT ECU (A540E)
or ECT ECU (A540H) connector to cancel out the diagnostic
(malfunction) code. (See page AT±192)
HINT:
wLow battery voltage will cause faulty operation of the diag-
nosis system. Therefore, always check the battery first.
wUse a voltmeter and ohmmeter that have an impedance of
at least 10 k
/V.
CHECK O/D OFF INDICATOR LIGHT
1. Turn the ignition switch ON.
2. The O/D OFF light will come on when the O/D switch
placed at OFF.
3. When the O/D switch is set to ON, the O/D OFF light should go
out.
If the O/D OFF light flashes when the O/D switch is set to
ON, the electronic control system is faulty.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±190

CANCEL OUT DIAGNOSTIC CODE
1. After repair of the trouble area, the diagnostic code
retained in memory by the Engine and ECT ECU (A540E)
or ECT ECU (A540H) must be canceled by removing the fuse EFI
(15A) (A540E) or DOME (20A) (A540H) for 10
seconds or more, depending on ambient temperature (the
lower the temperature, the longer the fuse must be left
out with the ignition switch OFF.
wHINT:Cancellation can be also done by removing the battery
negative (±) terminal, but in this case other memory systems
(engine control system diagnosis memory,
clock. ETR, etc.) will also be canceled out
wThe diagnostic code can be also canceled out by disconnect-
ing the Engine and ECT ECU (A540E) or ECT
ECU (A540H) connector.
wIf the diagnostic code is not canceled out, it will be retained
by the Engine and ECT ECU (A540E) or ECT
ECU (A540H) and appear along with a new code in
event of future trouble.
2. After cancellation, perform a road test to confirm that a
ºnormal codeº is now read on the O/D OFF indicator.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±193

TROUBLESHOOTING FLOW±CHART (A540E)
HINT:
wIf diagnostic code Nos. 42, 61, 62 or 63 are output, the overdrive OFF indicator light will begin to
blink immediately to warn the driver. However, an impact or shock may cause the blinking to stop;
but the code will still be retained in the Engine and ECT ECU memory until canceled out.
wThere is no warning for diagnostic code No. 64.
wIn the event of a simultaneous malfunction of both No. 1 and No. 2 speed sensors, no diagnostic
code will appear and the fail±safe system will not function. However, when driving in the D range,
the transaxle will not up±shift from first gear, regardless of the vehicle speed.
Check continuity between Engine and ECT
ECU connector SP, terminal and body ground.
(See page AT±216)
Check continuity between Engine and ECT
ECU connector SP2 terminal and body ground.
(See page AT±216)
1. Diagnostic code 42 (No. 1 speed sensor circuitry)
Check wiring between Engine and ECT ECU
and No. 2 speed sensor. Check wiring between Engine and ECT ECU
and combination meter.
2. Diagnostic code 61 (No. 2 speed sensor circuitry)
Check No. 2 speed sensor.
(See page AT±234) Substitute another Engine and ECT ECU.
Substitute another Engine and ECT ECU.Repair or replace No. 1 speed sensor.
Repair or replace No. 2
speed sensor. Check No. 1 speed sensor.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±194

Remove the oil pan and check resistance of
No. t solenoid valve connector and body ground.
Resistance: 11 ± 1 S
Remove the oil pan and check resistance of lock±
up solenoid valve connector and body ground.
Resistance: 11 ± 15 Remove the oil pan and check resistance of
No. 2 solenoid valve connector and body ground.
Resistance: 11 ± 15
Check resistance of lock±up solenoid valve at
Engine and ECT ECU connector.
(See page AT±216) Check resistance of No. 2 solenoid valve at
Engine and ECT ECU connector.
(See page AT±216) Check resistance of No. 1 solenoid valve at
Engine and ECT ECU connector
(See page AT±216)
Replace No. 1 and No. 2 solenoid
valves.
HINT: No. 1 and No. 2 solenoid valves
make a set.Replace No. 1 and No. 2 solenoid
valves.
HINT: No. 1 and No. 2 solenoid valves
make a set.
Check wiring between lock±up solenoid valve and
Engine and ECT ECU.Check wiring between No. 2 solenoid valve and
Engine and ECT ECU.Check wiring between No. 1 solenoid valve and
Engine and ECT ECU.
5. Diagnostic code 64 (Lock±up solenoid valve circuitry)3. Diagnostic code 62 (No. 1 solenoid valve circuitry)
4. Diagnostic code 63 (No. 2 solenoid valve circuitry)
Substitute another Engine and ECT ECU.
Substitute another Engine and ECT ECU.Substitute another Engine and ECT ECU.
Replace lock±up solenoid valve.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±195