ECU TOYOTA CAMRY V20 1986 Service Information

HINT:
wThe following troubleshooting procedures are designed for inspection of each separate system, and
therefore
the actual procedure may vary somewhat. However, troubleshooting should be performed while referring
to the inspection methods described in this manual.
wBefore beginning inspection, it is best to first make a simple check of the fuses, fusible links and the condi-
tion of the connectors.
wThe following troubleshooting procedures are based on the supposition that the trouble lies in either a
short or open circuit within the computer.
wIf engine trouble occurs even though proper operating voltage is detected in the computer connector,
then it can be assumed that the ECU is faulty and should be replaced. .
TROUBLESHOOTING WITH
VOLT OHMMETER
LOCATION OF FUSES AND FUSIBLE LINKS
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±31

EFI SYSTEM CHECK PROCEDURE
(3S±FE)
HINT:
wPerform all voltage measurements with the connectors con-
nected.
wVerify that the battery voltage is 11 V or more when the igni-
tion switch is in ºONº position.
Using a voltmeter with high impedance (10 kW/V minimum),
measure the voltage at each terminal of the wiring
connectors.
THROTTLE POSITION
SENSORTHROTTLE POSITION
SENSOR
THROTTLE POSITION
SENSOR
Terminals of ECU
NEUTRAL START
SWITCH
HEADLIGHT and
DEFOGGER EGR GAS TEMP.
SENSOR
WATER TEMP. SENSOR SUB±OXYGEN SENSORA/C MAGNET SWITCH
STOP LIGHT SWITCH
CHECK CONNECTORCHECK CONNECTORAIR FLOW METER
AIR FLOW METER
AIR FLOW METER STARTER SWITCH
SENSOR GROUND SENSOR GROUND ENGINE GROUND
ENGINE GROUND ENGINE GROUND
OXYGEN SENSOR
WARNING LIGHTA/C AMPLIFIER
SPEED SENSORTerminal name Terminal name Terminal name
DISTRIBUTORDISTRIBUTOR
DISTRIBUTOR
MAIN RELAYMAIN RELAY ISC VALVE
ISC VALVE INJECTORINJECTOR Symbol
BATTERY Symbol
Symbol
IGNITERECT ECUECT ECU
ECT ECU
IGNITER
ECT ECU
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±32

No trouble (ºCHECKº engine warning light off) and
engine running
Voltage at ECU Wiring Connectors (3S±FE)
Measuring plate fully closed
Intake air temp. 20°C (68°F)
Coolant temp. 80°C (1765F) Measuring plate fully open Throttle valve fully closed Throttle valve fully closed
Throttle valve open
Air conditioning ONThrottle valve open Throttle valve open
Cranking or idlingSTD voltage (V)
Terminals
3,000 rpmSee page Condition
IG SW ONIG SW ON
IG SW ON
IG
SW ONIG SW ON
IG SW ONCrankingIdling
FI±40
FI±44
FI±46FI±45FI±34
FI±43 FI±42
FI±47FI±35
FI±36
FI±37
FI±39
FI±41 No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±33

Check that there is voltage between ECU terminal +B or +B1 and
body ground. (IG SW ON) No voltage between ECU terminals +B or +B1 and El.
(IG SW ON)
Check wiring between ECU terminal E1 and body
ground.
Check wiring between ER main
relay and battery.Check fuse, fusible link and
ignition switch.
Check ER main relay.Try another ECU.
Repair or replace. Repair or replace.
Repair or replace.
Ignition SW ON
STD voltageTerminals
Condition
Replace.
Trouble
BAD BADBAD
BAD No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±34

Check that there is voltage between ECU terminal BATT and
body ground.
Check wiring between ECU terminal El and body
ground. No voltage between ECU terminals BATT and E1.
Check wiring between ECU
terminal and battery.Check fuse and fusible link.
Repair or replace.Repair or replace.
Try another ECU.STD voltage
No voltageCondition
Terminals
Replace. Trouble
BAD
BADBAD No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±35

Check that there is voltage between ECU terminal + B or + B1 and body
ground. (IG SW ON) No voltage between ECU terminal 1D1. or PSW and E1.
(IG SW ON)
Check wiring between ECU terminal El and body
ground.
Check wiring between ECU and
throttle position sensor. Check throttle position sensor.
(See page FI±106)
Replace or repair throttle
position sensor. Refer to No. 1.
(See page FI±34) Throttle valve fully closedThrottle valve open
Repair or replace.
Repair or replace.
Try another ECU.STD voltage
No voltageIG SW ONCondition
TerminalsTrouble
BAD
BAD
BAD
BAD No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±36

Check that there is voltage between ECU terminal +B or +B1 and body
ground. (IG SW 4111)
Check wiring between ECU terminal El and body
ground. No voltage between ECU terminals IDL and E2.
OG SW ON) (Throttle valve open)
Check wiring between ECU and
throttle position sensor. Check throttle position sensor.
(See page FI±110)
Repair or replace throttle
position sensor.Refer to No. 1.
(See page FI±34) Throttle valve fully closed
Throttle valve fully open
Try another ECU. Throttle valve open
Repair or replace.Repair or replace.
wIDL ± E2
STD voltage
No voltage
IG SW ON
Condition Terminals Trouble
BAD
BAD
BAD
BAD
No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±37

Check that there is voltage between ECU terminal +B or +131 and
body ground. (IG SW ON)
Check that there is voltage between ECU terminal VC and E2
(IG SW ON)No specified voltage at ECU terminals VTA and E2.
(IG SW ON) No voltage between ECU terminals VC and E2.
(IG SW ON)
Check wiring between ECU and throttle
position sensor.
Check wiring between ECU and
throttle position sensor.Check throttle position sensor
(See page FI±110) Check throttle position sensor.
(See page FI±110)
Repair or replace
wiring.
Refer to NO±1.
(See page FI±34)
Refer to VC±E2
trouble section
Repair or replace.
Repair or replace. Repair or replace.
Try another ECU.
Try another ECU.
wNTA ± E2 wVC±E2
BAD
BAD
BAD
BAD
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±38

Check that there is voltage between ECU terminal +B or +B1 and body
ground. (IG SW ON)No specified voltage at ECU terminals VC or VS and E2.
(IG SW ON)
Check wiring between ECU terminal E1 and body
ground.
Check wiring between ECU and air flow
meter. Check air flow meter.
(See page FI±104) Measuring plate fully closed
Refer to No. 1.
±(See page FI±34) Measuring plate fully open
Replace air flow
meter.
Repair or replace.Repair or replace.
Try another ECU.STD voltage
BAD 3,000 rpm N o voltageIG SW ON
TerminalsCondition
Trouble
Idling
BAD
BAD
No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±39

No voltage between ECU terminals No. 10 and/or No. 20 and
E01 and/or E02. (IG SW ON)
Check that there is voltage between ECU terminal No. 10
and/or No. 20 and body ground.
Check resistance of magnetic coil in each injector.
STD resistance: Approx. 13.8 11Check wiring between ECU terminal E01 and/or
E02 and body ground.
Check wiring between ECU
terminal No. 10 and/or No. 20
and battery.Check fuse, fusible link and
ignition switch.
Repair or replace. Repair or replace.
Repair or replace. Try another ECU.
Replace injector. STD voltage
No voltage
IG SW ONCondition
TerminalsTrouble
BAD BAD
BADBAD No.
± EFI SYSTEMTroubleshooting with Volt OhmmeterFI±40