ECU TOYOTA CAMRY V20 1986 Service Information

Is voltage between terminals OD2 and GND as fol-
lows?
O/D switch turn ON: 10 ± 14V
O/D switch turn OFF: 0VRoad test while shifting manually with solenoid
wire connector disconnected.
Is there overdrive up±shift in the D range
when shifting from L to 2 to D
Is voltage between Engine and ECT ECU
terminals OD, and E1 normal with the cruise con-
trol computer connector pulled out?Connect solenoid wire connector, and while driv-
ing does Tt terminal voltage rise from
0V to 7V in sequence?
Is voltage between terminals OD, and E, as fol-
lows?
Approx. 5 VAre there 10 ± 14V between Engine and
ECT ECU terminals L and E1 when in the D
range?
No up±shift to overdrive (After warm±up)
Are there 10 ± 14V between
Engine and ECT ECU terminals 2
and E1 when in the D range?
w Faulty Engine and ECT ECU
wFaulty cruise control wire harnessFaulty neutral start switch circuit
Faulty neutral start switch
Faulty O/D switch harness
Faulty O/D switch Try another Engine and ECT ECU
Try another Engine and ECT ECU
Faulty cruise control computerFaulty transaxle
Faulty solenoid Faulty transaxle
Trouble No. 3
Y
es
Ye s
Ye sYe s
Ye s Ye s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±209

Road test
Connect a voltmeter to terminals Tt and El.
Is there 7, 5 or 3V in the lock±up range while driv-
ing?
Is voltage between Engine and ECT ECU BK
and E1 terminals as follows?
Brake pedal depressed: 10 ± 14V
Brake pedal released: OV Warm up engine
Coolant temp.: 176°F (80°C)
ATF temp.: 122 ± 176°F (50 ± 80°C)
wFaulty ECU power source and ground
wFaulty throttle position signalwLock±up solenoid stuck
wFaulty transaxle
w Faulty lock±up mechanism
No lock±up (After warm±up)
Faulty brake signal
Trouble No. 4
Ye sYe s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±210

Disconnect solenoid wire connector and road test.
Does the transaxle operate in the respective gear
when in the following ranges white driving?
D range .... Overdrive
2 range .... Overdrive
L range .... 1 st gear
TROUBLESHOOTING FLOW±CHART (A540H)
Trouble No. 1 No Shifting
Is voltage between ECT ECU terminals BK
and GND as follows?
0V: Brake pedal released
10 ± 14V: Brake pedal depressed
Connect solenoid wire connector and road test.
Does Tt terminal voltage rise from OV to 7V in se-
quence?Warm up engine
Coolant temp.: 176°F (80°C)
ATF temp.: 122 ± 176°F (50 ± 80°)
Connect a voltmeter to terminals Tt and E1.
Does Tt terminal voltage vary with changes in
throttle opening? (See page AT±215)
wECU power source and ground faulty
wThrottle position signal faulty
wTt terminal wire open or short
Are there 10 ± 14V between ECT
ECU terminals 2L ± GND when in the
D range?
Are there 10 ± 14V between ECT ECU
terminals LL ± GND when in the D range?
wNeutral start switch circuit faulty
wNeutral start switch faultyProceed to trouble No. 3
(See page AT±227) Transaxle faulty
Solenoid faulty
Try another ECT ECUBrake signal
faulty
Transaxle faulty
Ye s
Ye s
Ye s Ye s
Ye s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±211

Is voltage between ECT ECU terminals BK
and GND as follows? .
0V: Brake pedal released
10 ± 14V: Brake pedal depressed
Check voltage between ECT ECU terminals
P and GND.
Power pattern: 10 ~ 14V
Normal pattern: 1 V Warm up engine
Coolant temp.: 176°F (80°C)
ATF temp.: 122 ± 176°F (50 ± 80°C)
Connect a voltmeter to terminals Tt and E1.
Does Tt terminal voltage vary with changes in
throttle opening? (Seepage AT±21 5)
ECU power source and ground faulty
Throttle position signal faulty
Tt terminal wire open or short
Faulty pattern select switch system
Shift point too high or too low
Faulty ECT ECU
Faulty speed sensorBrake signal
faulty
Trouble No. 2
Ye s
Ye s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±212

Disconnect the cruise control computer connector.
Is voltage between terminals 4D1 and GND
as follows?
Approx. 5VIs voltage between terminals OD2 and GND as fol-
lows?
O/D switch turn ON: 10 ± 14V
O/D switch turn OFF: 0VRoad test while shifting manually with solenoid
wire connector disconnected.
Is there overdrive up±shift in the D range when
shifting from L to 2 to D?
Is voltage between terminals OD1 and GND as
follows?
Approx. 5VConnect solenoid wire connector, and while driv-
ing does Tt terminal voltage rise from OV
to 7 V i n sequence?
Faulty ECT ECU
(Short circuit in ECT wire harness or EFI
water temp. sensor bad)Are there 10 ± 14V between ECT
ECU terminals LL and GND when in the
D range?
No up±shift to overdrive (After warm±up)
Are there 10 ± 14V between ECT
ECU terminals 2L and GND when in
the D range?
wFaulty neutral start switch circuit
wFaulty neutral start switch
wFaulty O/D switch circuit
wFaulty O/D switch
Faulty cruise control computerFaulty transaxle
Faulty solenoid
Try another ECT ECU Try another ECT ECUFaulty transaxle
Trouble No. 3
Ye sYe s
Ye s
Ye sYe s Ye s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±213

Road test
Connect a voltmeter to terminals Tt and E,.
Is there 7, 5 or 3V in the lock±up range while driv-
ing?
Is voltage between ECT ECU BK and GND
terminals as follows?
Brake pedal depressed: 10 ± 14V
Brake pedal released: OV Warm up engine
Coolant temp.: 176°F (80°C)
ATF temp.: 122 ± 176°F (50 ± 80°C)
Trouble No. 4 No lock±up (After warm±up)
w Lock±up solenoid stuck
wFaulty transaxle
wFaulty lock±up mechanism
wFaulty ECU power source and ground
wFaulty throttle position signalFaulty brake signal
Ye sYe s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±214

INSPECTION OF ELECTRONIC CONTROL
COMPONENTS
1. (A540E)
INSPECT VOLTAGE OF TCCS ECU CONNECTOR
(a) Turn on the ignition switch.
(b) Measure the voltage at each terminal.
Coolant temp. 176°F (84°C)
Cruise control main
switch OFFO/D main switch turned OFF O/D main switch turned ON Throttle valve fully closed
Throttle valve fully closed Brake pedal is depressed
Throttle valve fully openMeasuring condition
Brake pedal is released
Throttle valve open
Vehicle movingVehicle moving P, R or N range D, 2 or L range
Standing stillStanding still NORM patternVoltage (V)
PWR pattern Terminal
± AUTOMATIC TRANSAXLE(A540E and A540H)AT±216

2. (A540H)
INSPECT VOLTAGE OF ECT ECU CONNECTOR
(a) Turn on the ignition switch.
(b) Measure the voltage at each terminal.
Throttle valve fully closed to fully open
Throttle valve fully closed to fully openThrottle valve fully closedMeasuring conditionMeasuring condition
Throttle valve openExcept N rangeExcept R range
Except 2 range
Except L range
Voltage (V)Voltage IV1
R range Terminal
Terminal2 range N range
L range
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±217

3. (A540E)
INSPECT SOLENOID VALVES
(a) Disconnect the connector from Engine and ECT ECU
(b) Measure the resistance between S1, S2, SL and
body ground.
Resistance: 11 ± 15


(e) Apply battery voltage to each terminal.
Check that an operation noise can be heard from
the solenoid.
Center differential control switch AUTO position
Center differential control switch AUTO position Center differential control switch turned OFF
Center differential control switch turned OFF Coolant temp. below 122°F950°0 Throttle valve fully closed to fully open
Coolant temp. above 122°F (50°C0 O/D main switch turned OFF O/D main switch turned ON
Brake pedal is depressed
Brake pedal is releasedMeasuring condition
Except 2 range
Except N range Except P range
Except L range
NORM patternVoltage (V)
PWR pattern Terminal
N range2 range P range
L range
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±218

5. (A540H)
INSPECT CENTER DIFFERENTIAL CONTROL
SOLENOID VALVES
(a) Disconnect the connector from ECT ECU.
(b) Measure the resistance between SD1, SD2 and body ground.
Resistance: 11 ± 15


(c) Apply battery voltage to each terminal.
Check that an operation noise can be heard from± the sole-
noid.
6. CHECK SOLENOID SEALS
If there is foreign material in the solenoid valve, there will be no
fluid control even with solenoid operation.
(a) Check No. 1 and No. 2 solenoid valves. (A540E,
A540H)
wApplying 5 kg/cm2 (71 psi, 490 kPa) of compressed air,
check that the solenoid valves open do not leak the air.
wWhen supply battery voltage to the solenoids, check that the
solenoid valves open.
(b) Check the lock±up solenoid valve. (A540E, A540H)
wApplying 5 kglcm2 (71 psi, 490 kPa) of compressed air, check
that the solenoid valve opens.
wWhen supply battery voltage to the solenoid, check that the
solenoid valve does not leak the air. 4. (A540H)
INSPECT SOLENOID VALVES
(a) Disconnect the connector from ECT ECU.
(b) Measure the resistance between S1, S2, SL and body
ground.
Resistance: 11 ± 15


(c) Apply battery voltage to each terminal.
Check that an operation noise can be heard from the
solenoid.
(c) Check No. 1 and No. 2 center differential control
solenoid valves. (A540H)
wApplying 5 kg/cm2 (71 psi, 490 kPa) of com-
pressed air, check that the solenoid valves
open do not leak the air.
wWhen supply battery voltage to the solenoids,
check that the solenoid valves open.
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±219