ECU TOYOTA CAMRY V20 1986 Service Information

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

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