1996 TOYOTA T100 ECU

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FI0047
FI0048
IN02K−03
IN−26− INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
1996 TOYOTA T100 (RM449U)
HOW TO USE THE DIAGNOSTIC
CHART AND INSPECTION
PROCEDURE
1. CONNECTOR CONNECTION AND TERMINAL IN-
SPECTION
For troubleshooting, diagnostic trouble code charts or
problem symptom table are provided for each circuit with
detailed inspection procedures on the following pages.
When all the component parts, wire harnesses and con-
nectors of each circuit except the ECU are found to be
normal in troubleshooting, then it is determined that the
problem is in the ECU. Accordingly, if diagnosis is per-
formed without the problem symptoms occurring,refer to
step 8 to replace the ECU, even if the problem is not in the
ECU. So always confirm that the problem symptoms are
occurring, or proceed with inspection while using the
symptom simulation method.
The instructions ”Check wire harness and connector” and
”Check and replace ECU” which appear in the inspection
procedure, are common and applicable to all diagnostic
trouble codes. Follow the procedure outlined below
whenever these instructions appear.
OPEN CIRCUIT:
This could be due to and a disconnected wire harness, faulty
contact in the connector, a connector terminal pulled out, etc.
HINT:
It is rarely the case that a wire is broken in the middle of
it. Most cases occur at the connector. In particular, care-
fully check the connectors of sensors and actuators.
Faulty contact could be due to rusting of the connector
terminals, to foreign materials entering terminals or a de-
formation of connector terminals between the male and
female terminals of the connector. Simply disconnecting
and reconnecting the connectors once changes the
condition of the connection and may result in a return to
normal operation. Therefore, in troubleshooting, if no ab-
normality is found in the wire harness and connector
check, but the problem disappears after the check, then
the cause is considered to be in the wire harness or con-
nectors.
SHORT CIRCUIT:
This could be due to a connect between the wire harness and
the body ground or to a short occurred inside the switch etc.
HINT:
When there is a short circuit between the wire harness and body
ground, check thoroughly whether the wire harness is caught
in the body or is clamped properly.

Downloaded from www.Manualslib.com manuals search engine IN0379
Sensor Side
ECU Side
IN0378
Sensor SideECU Side
IN0380
Sensor SideECU Side
IN0381
Pull Lightly
Looseness of Crimping
− INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN−27
1996 TOYOTA T100 (RM449U)
2. CONTINUITY CHECK (OPEN CIRCUIT CHECK)
(a) Disconnect the connectors at both ECU and sensor
sides.
(b) Measure the resistance between the applicable terminals
of the connectors.
HINT:
Measure the resistance while lightly shaking the wire har-
ness vertically and horizontally.
When tester probes are inserted into a connector, insert
the probes from the back. For waterproof connectors in
which the probes cannot be inserted from the back, be
careful not to bend the terminals when inserting the tester
probes.
3. RESISTANCE CHECK (SHORT CIRCUIT CHECK)
(a) Disconnect the connectors on both ends.
(b) Measure the resistance between the applicable terminals
of the connectors and body ground. Be sure to carry out
this check on the connectors on both ends.
Resistance: 1 MΩ or higher
HINT:
Measure the resistance while lightly shaking the wire harness
vertically and horizontally.
4. VISUAL CHECK AND CONTACT PRESSURE CHECK
(a) Disconnect the connectors at both ends.
(b) Check for rust or foreign material, etc. in the terminals of
the connectors.
(c) Check crimped portions for looseness or damage and
check if the terminals are secured in lock portion.
HINT:
The terminals should not come out when pulled lightly.
(d) Prepare a test male terminal and insert it in the female ter-
minal, then pull it out.
NOTICE:
When testing a gold−plated female terminal, always use a
gold−plated male terminal.
HINT:
When the test terminal is pulled out more easily than others,
there may be poor contact in that section.

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Z17004
CB
AOPENSensor Fig. 1 ECU
1
21
21
221
Z17005
Fig. 2
SensorECU
C
BA1
21
21
2
B04722
Fig. 3
ECU
Sensor
21A B1 C
1
1
221
2 B2
IN−28− INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
1996 TOYOTA T100 (RM449U)
5. CONNECTOR HANDLING
When inserting tester probes into a connector, insert them from
the rear of the connector. When necessary, use mini test leads.
For water resistant connectors which cannot be accessed from
behind, take good care not to deform the connector terminals.
6. CHECK OPEN CIRCUIT
For the open circuit in the wire harness in Fig.1, perform ”(a)
Continuity Check” or ”(b) Voltage Check” to locate the section.
(a) Check the continuity.
(1) Disconnect connectors ”A” and ”C” and measure
the resistance between them.
In the case of Fig.2,
Between terminal 1 of connector ”A” and terminal 1
of connector ”C” → No continuity (open)
Between terminal 2 of connector ”A” and terminal 2
of connector ”C” → Continuity
Therefore, it is found out that there is an open circuit
between terminal 1 of connector ”A” and terminal 1
of connector ”C”.
(2) Disconnect connector ”B” and measure the resis-
tance between the connectors.
In the case of Fig.3,
Between terminal 1 of connector ”A” and terminal 1
of connector ”B1” → Continuity
Between terminal 1 of connector ”B2” and terminal
1 of connector ”C” → No continuity (open)
Therefore, it is found out that there is an open circuit
between terminal 1 of connector ”B2” and terminal
1 of connector ”C”.

Downloaded from www.Manualslib.com manuals search engine Z17007
Fig. 4
Sensor
CA1
21
21
2ECU
B
5 V
5 V0 V5 V
Z17008
CBASHORT
Fig. 5
1
21
22 1
Z17009
Fig. 6
SensorECU
CB
A1
21
21
2
− INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN−29
1996 TOYOTA T100 (RM449U)
(b) Check the voltage.
In a circuit in which voltage is applied (to the ECU connec-
tor terminal), an open circuit can be checked for by con-
ducting a voltage check.
As shown in Fig.4, with each connector still connected,
measure the voltage between body ground and terminal
1 of connector ”A” at the ECU 5V output terminal, terminal
1 of connector ”B”, and terminal 1 of connector ”C”, in that
order.
If the results are:
5V: Between Terminal 1 of connector ”A” and Body Ground
5V: Between Terminal 1 of connector ”B” and Body Ground
0V: Between Terminal 1 of connector ”C” and Body Ground
Then it is found out that there is an open circuit in the wire har-
ness between terminal 1 of ”B” and terminal 1 of ”C”.
7. CHECK SHORT CIRCUIT
If the wire harness is ground shorted as in Fig.5, locate the sec-
tion by conducting a ”continuity check with ground”.
Check the continuity with ground.
(1) Disconnect connectors ”A” and ”C” and measure
the resistance between terminal 1 and 2 of connec-
tor ”A” and body ground.
In the case of Fig.6
Between terminal 1 of connector ”A” and body
ground → Continuity (short)
Between terminal 2 of connector ”A” and body
ground → No continuity
Therefore, it is found out that there is a short circuit
between terminal 1 of connector ”A” and terminal 1
of connector ”C”.

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Fig. 7
SensorECU
C
A
1
21
21
221 B2 B1
IN0383
Example
Ground
IN0384
ECU Side
Ground
W/H Side
Ground
IN−30− INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
1996 TOYOTA T100 (RM449U)
(2) Disconnect connector ”B” and measure the resis-
tance between terminal 1 of connector ”A” and body
ground, and terminal 1 of connector ”B2” and body
ground.
Between terminal 1 of connector ”A” and body
ground → No continuity
Between terminal 1 of connector ”B2” and body
ground → Continuity (short)
Therefore, it is found out that there is a short circuit
between terminal 1 of connector ”B2” and terminal
1 of connector ”C”.
8. CHECK AND REPLACE ECU
First check the ECU ground circuit. If it is faulty, repair it. If it is
normal, the ECU could be faulty, so replace the ECU with a nor-
mal functioning one and check that the symptoms appear.
(1) Measure the resistance between the ECU ground
terminal and the body ground.
Resistance: 1 Ω or less
(2) Disconnect the ECU connector, check the ground
terminals on the ECU side and the wire harness
side for bend and check the contact pressure.

Downloaded from www.Manualslib.com manuals search engine IN02L−01
− INTRODUCTIONTERMS
IN−31
31 Author: Date:
1996 TOYOTA T100 (RM449U)
TERMS
ABBREVIATIONS USED IN THIS MANUAL
AbbreviationsMeaning
ABSAnti−Lock Brake System
A.D.D.Automatic Disconnecting Differential
A/TAutomatic Transmission
AT FAutomatic Transmission Fluid
BTDCBefore Top Dead Center
Calif.California
CBCircuit Breaker
Diff.LockDifferential Locking System
DPDash Pot
ECUElectronic Control Unit
E/GEngine
ELREmergency Locking Retractor
ESAElectronic Spark Advance
EXExhaust (Manifold, Valve)
FIPGFormed in Place Gasket
FLFusible Link
FPUFuel Pressure Up
FrFront
IGIgnition
INIntake (Manifold, Valve)
J/BJunction Block
LHLeft−Hand
LLCLong Life Coolant (Year Around Coolant)
LSPVLoad Sensing Proportioning Valve
Max.Maximum
Min.Minimum
MPMultipurpose
M/TManual Transmission
O/D, ODOverdrive
OHCOver Head Camshaft
O/SOversize
PCVPositive Crankcase Ventilation
PSPower Steering
RHRight−Hand
RrRear
SRSSupplemental Restraint System
SSMSpecial Service Materials
SSTSpecial Service Tools
STDStandard
SWSwitch
TDCTop Dead Center
TEMP.Temperature

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− INTRODUCTIONTERMS
IN−33
1996 TOYOTA T100 (RM449U)
GLOSSARY OF SAE AND TOYOTA TERMS
This glossary lists all SAE−J1930 terms and abbreviations used in this manual in compliance with SAE rec-
ommendations, as well as their Toyota equivalents.
SAE
ABBREVIATIONSSAE TERMSTOYOTA TERMS
( )−−ABBREVIATIONS
A/CAir ConditioningAir Conditioner
ACLAir CleanerAir Cleaner
AIRSecondary Air InjectionAir Injection (AI)
APAccelerator Pedal−
B+Battery Positive Voltage+B, Battery Voltage
BAROBarometric Pressure−
CACCharge Air CoolerIntercooler
CARBCarburetorCarburetor
CFIContinuous Fuel Injection−
CKPCrankshaft PositionCrank Angle
CLClosed LoopClosed Loop
CMPCamshaft PositionCam Angle
CPPClutch Pedal Position−
CTOXContinuous Trap Oxidizer−
CTPClosed Throttle Position−
DFIDirect Fuel Injection (Diesel)Direct Injection (DI)
DIDistributor Ignition−
DLC1
DLC2
DLC3Data Link Connector 1
Data Link Connector 2
Data Link Connector 31: Check Connector
2: Total Diagnosis Comunication Link (TDCL)
3: OBD II Diagnostic Connector
DTCDiagnostic Trouble CodeDiagnostic Code
DTMDiagnostic Test Mode−
ECLEngine Control Level−
ECMEngine Control ModuleEngine ECU (Electronic Control Unit)
ECTEngine Coolant TemperatureCoolant Temperature, Water Temperature (THW)
EEPROMElectrically Erasable Programmable Read Only Memory
Electrically Erasable Programmable Read Only Memory
(EEPROM),
Erasable Programmable Read Only Memory (EPROM)
EFEEarly Fuel EvaporationCold Mixture Heater (CMH), Heat Control Valve (HCV)
EGRExhaust Gas RecirculationExhaust Gas Recirculation (EGR)
EIElectronic IgnitionDistributorless Ignition (DI)
EMEngine ModificationEngine Modification (EM)
EPROMErasable Programmable Read Only MemoryProgrammable Read Only Memory (PROM)
EVAPEvaporative EmissionEvaporative Emission Control (EVAP)
FCFan Control−
FEEPROMFlash Electrically Erasable Programmable
Read Only Memory−
FEPROMFlash Erasable Programmable Read Only Memory−
FFFlexible Fuel−
FPFuel PumpFuel Pump
GENGeneratorAlternator
GNDGroundGround (GND)

Downloaded from www.Manualslib.com manuals search engine − INTRODUCTIONTERMS
IN−35
1996 TOYOTA T100 (RM449U) TCM
Transmission Control ModuleTransmission ECU (Electronic Control Unit)
TPThrottle PositionThrottle Position
TRTransmission Range−
TVVThermal Vacuum ValveBimetallic Vacuum Switching Valve (BVSV)
Thermostatic Vacuum Switching Valve (TVSV)
TWCThree−Way Catalytic ConverterThree−Way Catalytic (TWC)
CC
RO
TWC+OCThree−Way + Oxidation Catalytic ConverterCCR + CCo
VA FVolume Air FlowAir Flow Meter
VRVoltage RegulatorVoltage Regulator
VSSVehicle Speed SensorVehicle Speed Sensor (Read Switch Type)
WOTWide Open ThrottleFull Throttle
WU−OCWarm Up Oxidation Catalytic Converter−
WU−TWCWarm Up Three−Way Catalytic ConverterManifold Converter
3GRThird Gear−
4GRFourth Gear−