1986 TOYOTA CAMRY V20 ECU

TROUBLESHOOTING FLOW±CHART (A540H)
HINT:
wIf diagnostic code Nos. 44, 61, 62, 63, 73 or 74 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 ECT ECU memory until canceled out.
wThere is no warning for diagnostic code No. 64.
wIn the event of a simultaneous malfunction of both vehicle and rear 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.
1. Diagnostic code 44 (Rear speed sensor circuitry)
Check continuity between ECT ECU NC
Check continuity between ECT ECU
connector RR+ terminal and RR± terminal.
(See page AT±217)
Check continuity between ECT ECU
connector FR+ terminal and FR± terminal.
(See page AT±217)
Check wiring between ECT ECU and vehicle
speed sensor. Check wiring between ECT ECU and rear
wheel speed sensor.
2. Diagnostic code 61 (Vehicle speed sensor circuitry)Repair or replace rear wheel speed
sensor. Check rear wheel speed sensor.
(See page AT±221)
Check vehicle speed sensor.
(See page AT±221)Repair or replace vehicle
speed sensor. Substitute another ECT ECU. Substitute another ECT ECU.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±196

Remove the oil pan and check resistance of lock±
up solenoid valve connector and body ground.
Resistance: 11 ± 15 W Remove the oil pan and check resistance of
No. 2 solenoid valve connector and body ground.
Resistance: 11 ± 15 W Remove the oil pan and check resistance of
No. 1 solenoid valve connector and body ground.
Resistance: 11 ± 15
5. Diagnostic code 64 (Lock±up solenoid valve circuitry)4. Diagnostic code 63 (No. 2 solenoid valve circuitry)3. Diagnostic code 62 (No. 1 solenoid valve circuitry)
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 resistance of lock±up solenoid valve at
ECT ECU connector. (See page AT±219) Check resistance of No. 1 solenoid valve at
ECT ECU connector. (See page AT±219)
Check resistance of No. 2 solenoid valve at
ECT ECU connector. (See page AT±219)
Check wiring between lock±up solenoid valve and
ECT ECU.Check wiring between No. 1 solenoid valve and
ECT ECU.
Check wiring between No. 2 solenoid valve and
ECT ECU.
Replace lock±up solenoid valve. Substitute another ECT ECU.
Substitute another ECT ECU.
Substitute another ECT ECU.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±197

6. Diagnostic code 73 (No. 1 center differential control solenoid valve circuitly)
Replace No. 1 and No. 2 center differ-
ential control solenoid valves.
HINT: No. 1 and No. 2 center differen-
tial control solenoid valves make a
set. Check resistance of No. 2 center differential con-
trol solenoid valve connector and body ground.
Resistance: 11 ± 15 Check resistance of No. 1 center differential control
solenoid valve connector and body ground.
Resistance: 11 ± 15 WReplace No. 1 and No. 2 center differ-
ential control solenoid valves.
HINT: No. 1 and No. 2 center differen-
tial control solenoid valves make a
set.
Check resistance of No. 2 center differential control
solenoid valve at ECT ECU connector.
(See page AT±219) Check resistance of No. 1 center differential control
solenoid valve at ECT ECU connector.
(See page AT±219)
7. Diagnostic code 74 (No. 2 center differential control solenoid valve circuitly)
Check wiring between No. 2 center differential con-
trol solenoid valve and ECT ECU. Check wiring between No. 1 center differential con-
trol solenoid valve and ECT ECU. Substitute another ECT ECU.
Substitute another ECT ECU.
± AUTOMATIC TRANSAXLETroubleshooting (Diagnosis System) (A540E and A540H)AT±198

MEASURE CENTER DIFFERENTIAL CONTROL PRESSURE (A540H Only)
(a) Warm up the transaxle fluid (122 ± 176°F or 50 ± 80°C)
(b) Measure the line pressure. (See page AT±224)
(e) Remove the transfer case test plug and mount the oil pressure gauge (SST).
SST 09992±00094
(d) Check the parking brake to see that it is fully applied chock the four wheels.
(e) Disconnect the connector from ECT ECU.
(f) Start the engine.
(g) Apply battery voltage to terminal SD1, or SD2 of the wire harness side connector and turn the No. .1
and No. 2 center differential control solenoid valves to either ON or OFF.
(h) Shift into the L range, step down strongly on the brake pedal with your left foot and while manipulating the
accelerator pedal with the right foot, measure the pressure at the engine speeds specified in the table.
kg/cm2 (psi, kPa)
HINT: After inspecting the center differential control pressure, erase the diagnosis codes (No. 73 and 74)
from the memory.
Condition of
Solenoid
ValvesNo. 1 Solenoid
Valve
No. 2 Solenoid
Valve
Engine
RPML range
Range
Idling
Stall
± AUTOMATIC TRANSAXLETroubleshooting (Mechanical System Tests) (A540E and
A540H)AT±226

Disconnect solenoid wire connector and road test.
Does the transaxle operate in the respective gear
when in the following ranges while driving?
D range .... Overdrive
2 range .... Overdrive
L range .... 1 st gear
TROUBLESHOOTING FLOW±CHART (A540E)
Trouble No. 1 No Shifting
Is voltage between Engine and ECT ECU
terminals BK and E1 as follows?
0V: Brake pedal released
10 ± 14V: Brake pedal depressed
Connect solenoid wire connector and road test.
Does Tt terminal voltage rise from 0V to
7V in sequence?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? (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
Engine and ECT ECU terminals 2 ± E
when in the D range?
Are there 10 ± 14V between Engine and ECT
ECU terminals L ± Ex when in the D range?
wNeutral start switch circuit faulty
wNeutral start switch faultyProceed to trouble No. 3
(See page AT±209)
Try another Engine and ECT ECUw Transaxle faulty
wSolenoid faultyBrake signal faulty
Transaxle faulty
Ye s
Ye s
Ye s
Ye s Ye s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±207

Check voltage between Engine and ECT ECU
terminals PWR and E1.
Power pattern: 10 ± 14V
Normal pattern: 1VIs voltage between Engine and ECT ECU
terminals BK and E1 as follows?
0V: Brake pedal released
1V: Brake pedal depressed Warm up engine
Coolant temp.: 176°F (80°C)
ATF temp.: 122 ± 176°F (50 ± 80°C)
Connect a voltmeter to terminals Tt and El.
Does Tt terminal voltage vary with changes in
throttle opening? (See page AT±215)
ECU power source and ground faulty
Throttle position signal faulty
Tt terminal wire open or short
Faulty Engine and ECT ECU
Faulty transaxle
Shift point too high or too Low
Faulty pattern select switch systemBrake signal
faulty
Trouble No. 2
Ye s Ye s
± AUTOMATIC TRANSAXLETroubleshooting (Electronic Control System) (A540E and
A540H)AT±208

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